Systems including a condensing apparatus such as a bubble column condenser

ABSTRACT

Condensing apparatuses and their use in various heat and mass exchange systems are generally described. The condensing apparatuses, such as bubble column condensers, may employ a heat exchanger positioned external to the condensing vessel to remove heat from a bubble column condenser outlet stream to produce a heat exchanger outlet stream. In certain cases, the condensing apparatus may also include a cooling device positioned external to the vessel configured and positioned to remove heat from the heat exchanger outlet stream to produce a cooling device outlet stream. The condensing apparatus may be configured to include various internal features, such as a vapor distribution region and/or a plurality of liquid flow control weirs and/or chambers within the apparatus having an aspect ratio of at least 1.5. A condensing apparatus may be coupled with a humidifier to form part of a desalination system, in certain cases.

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119(e) to U.S.Provisional Patent Application Ser. No. 61/877,032, filed Sep. 12, 2013,and entitled “Systems Including a Bubble Column Condenser”; U.S.Provisional Patent Application Ser. No. 61/901,757, filed Nov. 8, 2013,and entitled “Systems Including a Bubble Column Condenser”; and U.S.Provisional Patent Application Ser. No. 61/907,629, filed Nov. 22, 2013,and entitled “Systems Including a Bubble Column Condenser”; each ofwhich is incorporated herein by reference in its entirety for allpurposes.

FIELD

Embodiments described herein generally relate to condensing apparatuses(e.g., bubble column condensers) and their use in various heat and massexchange systems.

BACKGROUND

Fresh water shortages are becoming an increasing problem around theworld, as demand for fresh water for human consumption, irrigation,and/or industrial use continues to grow. Various desalination methodsare capable of producing fresh water from seawater, brackish water,flowback water, water produced from an oil or gas extraction process,and/or waste water. For example, a humidification-dehumidification (HDH)process involves contacting a saline solution with dry air in ahumidifier, such that the air becomes heated and humidified. The heatedand humidified air is then brought into contact with cold water in adehumidifier (e.g., condenser), producing pure water and dehumidifiedair.

However, HDH processes often involve certain drawbacks. For example, dueto the use of a carrier gas in HDH systems, a large percentage ofnon-condensable gas (e.g., air) is generally present in the condensingstreams, which can cause heat and mass transfer rates in thedehumidifier to be very low. Also, the presence of a non-condensable gascan increase the thermal resistance to condensation of vapor on a coldsurface, thereby reducing the effectiveness of surface condensers.Additionally, the dehumidifier can sometimes require large amounts ofenergy to operate. Condensers with improved properties, such as, forexample, reduced power consumption and/or high heat and mass transferrates in the presence of non-condensable gases, are therefore desirable.

SUMMARY

Condensing apparatuses, such as bubble column condensers, and their usein various heat and mass exchange systems are disclosed. The subjectmatter of the present invention involves, in some cases, interrelatedproducts, alternative solutions to a particular problem, and/or aplurality of different uses of one or more systems and/or articles.

Certain embodiments relate to desalination systems. In some embodiments,a desalination system comprises a humidifier comprising a humidifierliquid inlet fluidically connected to a source of salt-containing water,a humidifier gas inlet fluidically connected to a source of a carriergas, and a humidifier outlet. In certain cases, the humidifier isconfigured to produce a vapor-containing humidifier outlet streamenriched in water vapor relative to the gas received from the gas inlet.In some embodiments, the desalination system comprises a bubble columncondenser comprising a condenser inlet fluidically connected to thehumidifier outlet, a condenser gas outlet, and a condenser water outlet.In certain embodiments, the bubble column condenser is configured toremove at least a portion of the water vapor from the humidifier outletstream to produce a condenser gas outlet stream lean in water relativeto the humidifier outlet stream and a condenser water outlet stream. Insome embodiments, the desalination system comprises a heat exchangerseparate from the bubble column condenser and fluidically connected tothe condenser water outlet and configured to remove heat from thecondenser water outlet stream.

In some embodiments, the desalination system comprises a humidifiercomprising a humidifier liquid inlet fluidically connected to a sourceof salt-containing water, a humidifier gas inlet fluidically connectedto a source of a gas, and a humidifier outlet, wherein the humidifier isconfigured to produce a vapor-containing humidifier outlet streamenriched in water vapor relative to the gas received from the gas inlet.In certain embodiments, the desalination system comprises a bubblecolumn condenser comprising a condenser inlet fluidically connected tothe humidifier outlet, a condenser gas outlet, and a condenser wateroutlet, wherein the bubble column condenser is configured to remove atleast a portion of the water vapor from the humidifier outlet stream toproduce a condenser gas outlet stream lean in water relative to thehumidifier outlet stream and a condenser water outlet stream. In someembodiments, the desalination system comprises a heat exchangerfluidically connected to the condenser water outlet and configured toremove heat from the condenser water outlet stream. In certain cases, aportion of a gas flow is extracted from at least one intermediatelocation in the humidifier and fed from each of said at least oneintermediate location to a corresponding intermediate location in thebubble column condenser.

Certain embodiments relate to condenser systems comprising a bubblecolumn condenser comprising a vessel comprising an inlet in fluidcommunication with a source of a gas comprising a condensable fluid invapor phase, and an outlet, wherein the vessel contains a liquid layercomprising an amount of the condensable fluid and the bubble columncondenser is configured to remove at least a portion of the condensablefluid from the gas to produce a bubble column condenser outlet streamcomprising the condensable fluid in liquid phase. In some embodiments,the condenser systems further comprise a heat exchanger positionedexternal to the vessel and fluidically connected to the vessel toreceive the bubble column condenser outlet stream and to remove heatfrom the bubble column condenser outlet stream.

Some embodiments relate to a bubble column condenser comprising a firststage comprising a first stage inlet in fluid communication with asource of a gas comprising a condensable fluid in a vapor phase, and afirst stage outlet, wherein the first stage contains a liquid layercomprising an amount of the condensable fluid, and the ratio of theheight of the liquid layer within the first stage to the length of thecondenser is about 1.0 or lower during substantially continuousoperation.

In certain embodiments, the bubble column condenser comprises a firststage comprising a first stage inlet in fluid communication with asource of a gas comprising a condensable fluid in a vapor phase, and afirst stage outlet, wherein the first stage contains a liquid layercomprising an amount of the condensable fluid, the liquid layer having aheight of less than about 0.1 m during substantially continuousoperation.

In some embodiments, a condenser apparatus is provided. In some cases,the condenser apparatus comprises a vessel comprising a liquid inlet forreceiving a stream of a liquid comprising a condensable fluid in liquidphase, a liquid outlet, and at least one chamber in fluid communicationwith the liquid inlet and the liquid outlet. In certain embodiments, theat least one chamber comprises a bottom surface comprising a pluralityof perforations through which vapor can travel. In certain cases, thecondenser apparatus comprises a liquid layer positioned in contact withthe liquid outlet. In some cases, the liquid layer comprises an amountof the liquid comprising the condensable fluid. In some embodiments, thecondenser apparatus comprises a vapor distribution region positionedbelow the at least one chamber. According to some embodiments, the vapordistribution region comprises a vapor inlet in fluid communication witha source of a vapor mixture comprising the condensable fluid in vaporphase and/or a non-condensable gas. In some cases, the condenserapparatus comprises a vapor outlet arranged in fluid communication withthe at least one chamber. In certain embodiments, the condenserapparatus is configured to remove at least a portion of the condensablefluid from the vapor mixture to produce a condenser outlet streamcomprising the condensable fluid in liquid phase.

In some embodiments, a humidifier apparatus is provided. In some cases,the humidifier apparatus comprises a vessel comprising a liquid inletfor receiving a stream of a liquid comprising a condensable fluid inliquid phase, a liquid outlet, and at least one chamber in fluidcommunication with the liquid inlet and the liquid outlet. In certainembodiments, the at least one chamber comprises a bottom surfacecomprising a plurality of perforations through which vapor can travel.In certain cases, the humidifier apparatus comprises a liquid layerpositioned in contact with the liquid outlet. In some cases, the liquidlayer comprises an amount of the liquid comprising the condensablefluid. In some embodiments, the humidifier apparatus comprises a vapordistribution region positioned below the at least one chamber. Accordingto some embodiments, the vapor distribution region comprises a vaporinlet in fluid communication with a source of a vapor mixture comprisingthe condensable fluid in vapor phase and/or a non-condensable gas. Insome cases, the humidifier apparatus comprises a vapor outlet arrangedin fluid communication with the at least one chamber. In certainembodiments, the humidifier apparatus is configured to produce avapor-containing humidifier outlet stream enriched in the condensablefluid in vapor phase relative to the vapor mixture received from thevapor inlet.

Some embodiments relate to a condenser apparatus comprising a vesselcomprising a liquid inlet for receiving a stream of a liquid comprisinga condensable fluid in liquid phase, a liquid outlet, and at least onechamber in fluid communication with the liquid inlet and the liquidoutlet. In some cases, the at least one chamber has an aspect ratio ofat least 1.5. In some embodiments, the condenser apparatus comprises avapor inlet arranged in fluid communication with the at least onechamber and with a source of a vapor mixture comprising the condensablefluid in vapor phase and/or a non-condensable gas. In some embodiments,the condenser apparatus comprises a vapor outlet arranged in fluidcommunication with the at least one chamber. In certain cases, the atleast one chamber comprises a surface comprising a plurality ofperforations through which vapor can travel. In some embodiments, the atleast one chamber comprises a first weir and a second weir, eachpositioned along a bottom surface of the at least one chamber and eachhaving a height that is less than the height of the at least onechamber. In certain embodiments, the first weir and second weir arearranged such that the stream of the liquid comprising the condensablefluid in liquid phase flows across the at least one chamber from thefirst weir to the second weir. In certain embodiments, the condenserapparatus is configured to remove at least a portion of the condensablefluid from the vapor mixture to produce a condenser outlet streamcomprising the condensable fluid in liquid phase.

According to some embodiments, a humidifier apparatus comprises a vesselcomprising a liquid inlet for receiving a stream of a liquid comprisinga condensable fluid in liquid phase, a liquid outlet, and at least onechamber in fluid communication with the liquid inlet and the liquidoutlet. In some cases, the at least one chamber has an aspect ratio ofat least 1.5. In some embodiments, the humidifier apparatus comprises avapor inlet arranged in fluid communication with the at least onechamber and with a source of a vapor mixture comprising the condensablefluid in vapor phase and/or a non-condensable gas. In some embodiments,the humidifier apparatus comprises a vapor outlet arranged in fluidcommunication with the at least one chamber. In certain cases, the atleast one chamber comprises a surface comprising a plurality ofperforations through which vapor can travel. In some embodiments, the atleast one chamber comprises a first weir and a second weir, eachpositioned along a bottom surface of the at least one chamber and eachhaving a height that is less than the height of the at least onechamber. In certain embodiments, the first weir and second weir arearranged such that the stream of the liquid comprising the condensablefluid in liquid phase flows across the at least one chamber from thefirst weir to the second weir. In certain embodiments, the humidifierapparatus is configured to produce a vapor-containing humidifier outletstream enriched in the condensable fluid in vapor phase relative to thevapor mixture received from the vapor inlet.

Certain embodiments relate to a condenser apparatus comprising a vesselcomprising a liquid inlet for receiving a stream of a liquid comprisinga condensable fluid in liquid phase, a liquid outlet, and a plurality ofchambers arranged in a vertical manner with respect to one another andin fluid communication with the liquid inlet and the liquid outlet. Insome embodiments, the plurality of chambers comprises a first chambercomprising a top surface arranged in fluid communication with the liquidinlet and a bottom surface comprising a plurality of perforationsthrough which vapor can travel. In some embodiments, the plurality ofchambers further comprises a second chamber arranged below the firstchamber and in fluid communication with the first chamber. In certaincases, the second chamber comprises a plurality of perforations throughwhich vapor can travel. In some embodiments, the condenser apparatuscomprises a vapor inlet arranged in fluid communication with theplurality of chambers and with a source of a vapor mixture comprising acondensable fluid in vapor phase and/or a non-condensable gas. In somecases, the condenser apparatus comprises a vapor outlet arranged influid communication with the plurality of chambers. In certainembodiments, the first and second chambers are arranged such that thestream of the liquid comprising the condensable fluid in liquid phaseflows across the length of the first chamber in a first direction andacross the length of the second chamber in a second, opposing direction.In certain embodiments, the condenser apparatus is configured to removeat least a portion of the condensable fluid from the vapor mixture toproduce a condenser outlet stream comprising the condensable fluid inliquid phase.

In some embodiments, a humidifier apparatus comprises a vesselcomprising a liquid inlet for receiving a stream of a liquid comprisinga condensable fluid in liquid phase, a liquid outlet, and a plurality ofchambers arranged in a vertical manner with respect to one another andin fluid communication with the liquid inlet and the liquid outlet. Insome embodiments, the plurality of chambers comprises a first chambercomprising a top surface arranged in fluid communication with the liquidinlet and a bottom surface comprising a plurality of perforationsthrough which vapor can travel. In some embodiments, the plurality ofchambers further comprises a second chamber arranged below the firstchamber and in fluid communication with the first chamber. In certaincases, the second chamber comprises a plurality of perforations throughwhich vapor can travel. In some embodiments, the humidifier apparatuscomprises a vapor inlet arranged in fluid communication with theplurality of chambers and with a source of a vapor mixture comprising acondensable fluid in vapor phase and/or a non-condensable gas. In somecases, the humidifier apparatus comprises a vapor outlet arranged influid communication with the plurality of chambers. In certainembodiments, the first and second chambers are arranged such that thestream of the liquid comprising the condensable fluid in liquid phaseflows across the length of the first chamber in a first direction andacross the length of the second chamber in a second, opposing direction.In certain embodiments, the humidifier apparatus is configured toproduce a vapor-containing humidifier outlet stream enriched in thecondensable fluid in vapor phase relative to the vapor mixture receivedfrom the vapor inlet.

In some embodiments, a condenser apparatus is provided comprising avessel comprising a liquid inlet for receiving a stream of a liquidcomprising a condensable fluid in liquid phase, a liquid outlet, and aplurality of chambers arranged in a vertical manner with respect to oneanother and in fluid communication with the liquid inlet and the liquidoutlet. In certain cases, each chamber has an aspect ratio of at least1.5. In some embodiments, the plurality of chambers comprises a firstchamber comprising a top surface arranged in fluid communication withthe liquid inlet and a bottom surface comprising a plurality ofperforations through which vapor can travel, and a second chamberarranged below the first chamber and in fluid communication with thefirst chamber, the second chamber comprising a plurality of perforationsthrough which vapor can travel. In some embodiments, the condenserapparatus comprises a liquid layer positioned in contact with the liquidoutlet. In certain cases, the liquid layer comprises an amount of theliquid comprising the condensable fluid. In certain embodiments, thecondenser apparatus comprises a vapor distribution region positionedbelow the plurality of chambers. In some cases, the vapor distributionregion comprises a vapor inlet in fluid communication with a source of avapor mixture comprising a condensable fluid in vapor phase and/or anon-condensable gas. In some embodiments, the condenser apparatuscomprises a vapor outlet arranged in fluid communication with theplurality of chambers. In some embodiments, each of the first chamberand the second chamber comprises a first weir and a second weirpositioned along a bottom surface of the first or second chamber. Insome cases, the first weir and second weir each have a height that isless than the height of the first or second chamber. In some cases, thefirst and second weirs are arranged such that the stream of the liquidcomprising the condensable fluid in liquid phase flows across thechamber from the first weir to the second weir. In some embodiments, thefirst and second chambers are arranged such that the stream of theliquid comprising the condensable fluid in liquid phase flows across thelength of the first chamber in a first direction and across the lengthof the second chamber in a second, opposing direction. In certainembodiments, the condenser apparatus is configured to remove at least aportion of the condensable fluid from the vapor mixture to produce acondenser outlet stream comprising the condensable fluid in liquidphase.

In some embodiments, a humidifier apparatus is provided comprising avessel comprising a liquid inlet for receiving a stream of a liquidcomprising a condensable fluid in liquid phase, a liquid outlet, and aplurality of chambers arranged in a vertical manner with respect to oneanother and in fluid communication with the liquid inlet and the liquidoutlet. In certain cases, each chamber has an aspect ratio of at least1.5. In some embodiments, the plurality of chambers comprises a firstchamber comprising a top surface arranged in fluid communication withthe liquid inlet and a bottom surface comprising a plurality ofperforations through which vapor can travel, and a second chamberarranged below the first chamber and in fluid communication with thefirst chamber, the second chamber comprising a plurality of perforationsthrough which vapor can travel. In some embodiments, the humidifierapparatus comprises a liquid layer positioned in contact with the liquidoutlet. In certain cases, the liquid layer comprises an amount of theliquid comprising the condensable fluid. In certain embodiments, thehumidifier apparatus comprises a vapor distribution region positionedbelow the plurality of chambers. In some cases, the vapor distributionregion comprises a vapor inlet in fluid communication with a source of avapor mixture comprising a condensable fluid in vapor phase and/or anon-condensable gas. In some embodiments, the humidifier apparatuscomprises a vapor outlet arranged in fluid communication with theplurality of chambers. In some embodiments, each of the first chamberand the second chamber comprises a first weir and a second weirpositioned along a bottom surface of the first or second chamber. Insome cases, the first weir and second weir each have a height that isless than the height of the first or second chamber. In some cases, thefirst and second weirs are arranged such that the stream of the liquidcomprising the condensable fluid in liquid phase flows across thechamber from the first weir to the second weir. In some embodiments, thefirst and second chambers are arranged such that the stream of theliquid comprising the condensable fluid in liquid phase flows across thelength of the first chamber in a first direction and across the lengthof the second chamber in a second, opposing direction. In certainembodiments, the humidifier apparatus is configured to produce avapor-containing humidifier outlet stream enriched in the condensablefluid in vapor phase relative to the vapor mixture received from thevapor inlet.

Other advantages and novel features of the present invention will becomeapparent from the following detailed description of various non-limitingembodiments of the invention when considered in conjunction with theaccompanying figures. In cases where the present specification and adocument incorporated by reference include conflicting and/orinconsistent disclosure, the present specification shall control. If twoor more documents incorporated by reference include conflicting and/orinconsistent disclosure with respect to each other, then the documenthaving the later effective date shall control.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments of the present invention will be described byway of example with reference to the accompanying figures, which areschematic and are not intended to be drawn to scale. In the figures,each identical or nearly identical component illustrated is typicallyrepresented by a single numeral. For purposes of clarity, not everycomponent is labeled in every figure, nor is every component of eachembodiment of the invention shown where illustration is not necessary toallow those of ordinary skill in the art to understand the invention. Inthe figures:

FIG. 1A shows, according to some embodiments, an exemplarycross-sectional schematic illustration of a single-stage bubble columncondenser;

FIG. 1B shows, according to some embodiments, an exemplary top-down viewof a stage of a bubble column condenser;

FIG. 2A shows an exemplary cross-sectional schematic illustration of atwo-stage bubble column condenser without an intermediate gas inlet,according to some embodiments;

FIG. 2B shows an exemplary cross-sectional schematic illustration of atwo-stage bubble column condenser with an intermediate gas inlet,according to some embodiments;

FIG. 2C shows an exemplary cross-sectional schematic illustration of atwo-stage bubble column condenser with a vapor distribution chamber,according to some embodiments;

FIG. 2D shows an exemplary cross-sectional schematic illustration of atwo-stage bubble column condenser with a vapor distribution chamber andan intermediate gas inlet, according to some embodiments;

FIG. 3A shows, according to some embodiments, an exemplary schematicdiagram of a bubble column condenser and an external heat exchanger;

FIG. 3B shows, according to some embodiments, an exemplary schematicdiagram of a bubble column condenser, an external heat exchanger, anexternal heating device, and an external cooling device;

FIG. 4A shows an exemplary schematic diagram of an HDH system includinga bubble column condenser and an external heat exchanger, according tosome embodiments, where the external heat exchanger is a parallel flowdevice;

FIG. 4B shows, according to some embodiments, an exemplary schematicdiagram of an HDH system including a bubble column condenser and anexternal heat exchanger, where the external heat exchanger is a counterflow device;

FIG. 4C shows, according to some embodiments, an exemplary schematicdiagram of an HDH system including a bubble column condenser, anexternal heat exchanger, a first external heating device, and a secondexternal heating device;

FIG. 5 shows an exemplary schematic diagram of an eight-stage bubblecolumn condenser and an external heat exchanger, according to someembodiments;

FIG. 6 shows an exemplary embodiment of a baffled bubble-generatingchamber with two passes of liquid cross flow;

FIG. 7A shows an exemplary embodiment of a multi-stage bubble columncondenser in closed isometric view;

FIG. 7B shows a cross-sectional isometric view of the exemplaryembodiment of a multi-stage bubble column condenser shown in FIG. 7A;

FIGS. 7C-F show two-dimensional side-view or top-view projections of theexemplary embodiment of a multi-stage bubble column condenser shown inFIG. 7A;

FIG. 7G shows various views of the top surface of the exemplaryembodiment of a multi-stage bubble column condenser shown in FIG. 7A;

FIG. 7H shows various views of a bubble-generating chamber with one passof liquid cross flow in the exemplary embodiment of a multi-stage bubblecolumn condenser shown in FIG. 7A;

FIG. 7I shows a top-down view of a portion of a bubble-generatingchamber in the exemplary embodiment of a multi-stage bubble columncondenser shown in FIG. 7A;

FIG. 8 shows an exemplary cross-sectional schematic illustration of asingle-stage bubble column condenser comprising a stack to reduce oreliminate droplet entrainment, according to some embodiments;

FIG. 9 shows, according to some embodiments, an exemplary schematicdiagram of an HDH system including a bubble column condenser, a heatexchanger, a first heating device, a second heating device, and acooling device;

FIG. 10A shows, according to some embodiments, an exemplary schematicillustration of an eight-stage bubble column condenser and an externalheat exchanger;

FIG. 10B shows, according to some embodiments, an exemplary schematicillustration of an eight-stage bubble column condenser, an external heatexchanger, and an external cooling device;

FIG. 11A shows, according to some embodiments, an exemplary schematicillustration of an HDH system comprising a bubble column condenser, ahumidifier, an external heat exchanger, an external heating device, andan external cooling device;

FIG. 11B shows, according to some embodiments, an exemplary schematicillustration of an HDH system comprising a bubble column condensercomprising an intermediate air inlet, a humidifier comprising anintermediate air outlet, an external heat exchanger, an external heatingdevice, and an external cooling device;

FIG. 11C shows, according to some embodiments, an exemplary schematicillustration of an HDH system comprising a bubble column condensercomprising an internal heat exchanger, a humidifier, an external heatingdevice, and an external cooling device;

FIG. 11D shows, according to some embodiments, an exemplary schematicillustration of an HDH system comprising a bubble column condensercomprising an internal heat exchanger and an intermediate air inlet, ahumidifier comprising an intermediate air outlet, an external heatingdevice, and an external cooling device;

FIG. 12 shows, according to some embodiments, an exemplary schematicillustration of a chamber having a substantially circular cross sectionand comprising a spiral baffle; and

FIG. 13 shows an exemplary schematic illustration of a chamber having asubstantially circular cross section and comprising two baffles,according to some embodiments.

DETAILED DESCRIPTION

Embodiments described herein provide condensing apparatuses (e.g.,bubble column condensers) and their use in various heat and massexchange systems. For example, the condensing apparatuses may be usefulin systems for purification of water (e.g., desalination systems). Insome cases, the condensing apparatuses allow for simplified, lower costsystems with improved performance, such as improved heat and massexchange between gas and liquid phases. It should be noted that whilethe apparatuses described herein are generally referred to as condensingapparatuses or condensers, the apparatuses may, in some cases, be usedfor humidification. For example, certain of the embodiments describedherein may relate to bubble column humidifiers.

In some cases, the condensers may advantageously allow for a reducednumber of components, a reduced amount of material (e.g., heat transfersurface area) within a system, a reduced cost of components, and/orcomponents having reduced dimensions. For example, a system may includea component containing an amount of a liquid at a certain height, andincorporation of condensers described herein may allow for a reductionin the amount, and, hence, height, of the liquid within the component.In some cases, reducing the amount of liquid within the system may allowfor more simplified components having reduced dimensions with similaror, in some cases, improved performance relative to larger systems. Forexample, a component may be useful in facilitating heat transfer betweengas and liquid phases within the condenser. Incorporation of suchcomponents having reduced dimensions (e.g., height, stage spacing, etc.)within a single condenser may allow for use of a greater number ofcomponents within a given condenser, resulting in increased heat andmass exchange between the gas and liquid phases. Additionally, theamount of materials required to construct condensers described hereinmay be reduced, thereby reducing cost of fabrication. Further, incertain embodiments of the condensers described herein, heat and masstransfer occurs through bubbles of a gas or gas mixture (e.g., heat andmass may be transferred from bubbles of a gas or gas mixture comprisinga condensable fluid in vapor phase to a liquid bath of the condensablefluid through a condensation process). The use of gas bubbles ratherthan, for example, metallic surfaces (e.g., titanium tubes) for heat andmass transfer may advantageously reduce the fabrication cost of thecondensers. Further, the use of gas bubbles may increase the amount ofsurface area available for heat and mass transfer, thereby resulting inan advantageous increase in the thermodynamic effectiveness of thebubble column condensers.

In some cases, condensers described herein may advantageously exhibit areduced pressure drop across the condenser. That is, the pressure at aninlet of the condenser may be substantially the same as (e.g., less than10% variation from) the pressure at an outlet of the condenser. Forexample, the pressure of a fluid (e.g., vapor) entering an inlet of thecondenser may be substantially the same as the pressure of the fluidexiting an outlet of the condenser. Reduction of the pressure dropacross the condenser may be advantageous in that a relatively smallerpump, requiring less power and cost to operate, may be used to pumpfluids through the condenser.

Condensers described herein may, in some embodiments, exhibit improvedheat transfer properties, a characteristic that may be particularlyadvantageous in cases where the material passing through the condenserincludes a non-condensable gas. Non-condensable gases generally refer toany gas that does not condense into a liquid phase under the operatingconditions of the condenser. Examples of non-condensable gases include,but are not limited to, air, nitrogen, oxygen, and helium. In somecases, the condenser may be configured such that heat transfer rates areimproved for mixtures including a non-condensable gas.

Typically, the condenser may be configured to receive a condenser liquidinlet stream and to deliver a condenser liquid outlet stream to anothercomponent within a system. The condenser may also be configured toreceive a gas or gas mixture via at least one inlet and to deliver a gasor gas mixture via an outlet to another component within the system. Insome embodiments, the gas or gas mixture may comprise a vapor mixture(e.g., a condensable fluid in vapor phase and/or a non-condensable gas).In some cases, the gas or gas mixture entering the condenser may have adifferent composition than the gas or gas mixture exiting the condenser.For example, the gas or gas mixture entering the condenser may include aparticular fluid (e.g., a condensable fluid), a portion of which may beremoved in the condenser such that the exiting gas or gas mixture has arelatively decreased amount of the fluid. In some embodiments, the fluidmay be removed from the gas or gas mixture via a condensation process.In some cases, the condenser may be a bubble column condenser, whereinvapors are condensed in a column of relatively cold liquid. In someembodiments, the bubble column condenser comprises at least one stagewithin which a gas or gas mixture is treated such that one or morecomponents of the gas or gas mixture is removed. For example, the gas orgas mixture may include a condensable fluid in vapor phase, and recoveryof the condensable fluid (e.g., in liquid form) may be performed withinthe at least one stage of the bubble column condenser. A condensablefluid generally refers to a fluid that is able to condense from gasphase to liquid phase under the operating conditions of the condenser.

FIG. 1A shows an exemplary cross-sectional diagram of a single-stagebubble column condenser. As shown in FIG. 1A, bubble column condenser100 includes stage 110, which includes inlet 120, outlet 130, andchamber 140 (e.g. as provided by a containing vessel). Liquid layer 150,which comprises a condensable fluid in a liquid phase, resides inchamber 140. As an illustrative embodiment, the condensable fluid may bewater. Liquid layer 150 may, in some embodiments, have a height H_(L)that is relatively low (e.g., about 0.1 m or less). Height H_(L) may beless than a height H_(C) of chamber 140. In some cases, the portion ofchamber 140 that is not occupied by liquid layer 150 comprises a vapordistribution region. Inlet 120 is in fluid communication with a sourceof a gas or gas mixture containing a condensable fluid in a vapor phase.In some embodiments, the gas may further contain one or morenon-condensable gases. For example, the gas may include humidified air.Inlet 120 may also be coupled to bubble generator 160 such that gasentering inlet 120 is fed into bubble generator 160. As discussed infurther detail below, the bubble generator may comprise a sparger platecomprising a plurality of holes. Bubble generator 160 may be in fluidcommunication with chamber 140 and/or may be arranged within chamber140. In some cases, bubble generator 160 forms the bottom surface ofchamber 140.

In some cases, inlets and/or outlets within the column may be providedas separate and distinct features (e.g., inlet 120 in FIG. 1A). In somecases, inlets and/or outlets within the column may be provided bycertain components such as the bubble generator, sparger plate, and/orany other features which establish fluid communication betweencomponents of the column and/or system. For example, the “inlet” of aparticular stage of the column may be provided as the plurality of holesof a sparger plate. For example, a gas or gas mixture travelling betweena first and second stage may enter the second stage via an “inlet”provided by holes of a sparger plate.

When the bubble column condenser is in operation, the gas or gas mixtureflows through inlet 120 to bubble generator 160, producing gas bubbles170 that contain the gas or gas mixture and travel through liquid bath(e.g., liquid layer) 150. The temperature of liquid bath 150 may bemaintained lower than the temperature of gas bubbles 170, resulting intransfer of heat and mass from gas bubbles 170 to liquid bath 150through a condensation process. After passing through liquid bath 150,the gas or gas mixture, which has been at least partially dehumidified,may enter the vapor distribution region (e.g., the portion of chamber140 that is not occupied by liquid bath 150). In some cases, the gas orgas mixture may be substantially homogeneously distributed throughoutthe vapor distribution region. The gas or gas mixture may then proceedto exit the bubble column condenser through outlet 130. In an exemplaryembodiment, a gas mixture containing water and air may be passed throughbubble column condenser 100 such that gas bubbles 170 are formedcontaining both water in vapor form and air. Upon contact with liquidbath 150, water may then be condensed and transferred to liquid bath150, thereby producing a dehumidified gas that exits bubble columncondenser 100 via outlet 130.

In some embodiments, the pressure of the gas or gas mixture at inlet 120is substantially the same as the pressure of the gas or gas mixture atoutlet 130. In some embodiments, the pressure of the gas or gas mixtureat inlet 120 differs from the pressure of the gas or gas mixture atoutlet 130 by about 1 kPa or less. In some embodiments, the pressure ofthe gas or gas mixture at inlet 120 is less than about 1 kPa larger thanthe pressure of the gas or gas mixture at outlet 130.

As shown in FIG. 8, bubble column condenser 100 may further comprise anoptional stack 800 in fluid communication with outlet 130. Stack 800 maybe added, for example, to reduce or eliminate droplet entrainment (e.g.,droplets of liquid from liquid bath 150 flowing out of outlet 130 withthe dehumidified gas). In certain embodiments, bubble column condenser100 may comprise an optional droplet eliminator (not shown in FIG. 8).The droplet eliminator may, for example, comprise a mesh extendingacross the cross section of bubble column condenser 100. In operation,entrained liquid droplets may collide with the mesh and return to liquidbath 150. In some cases, reducing or eliminating droplet entrainment mayadvantageously increase the amount of purified water recovered frombubble column condenser 100 (e.g., by reducing the amount of purifiedwater that exits bubble column condenser 100 into the ambient air). Incertain embodiments, reducing or eliminating droplet entrainment mayincrease the amount of purified water recovered from bubble columncondenser 100 by at least about 1%, at least about 5%, at least about10%, at least about 15%, at least about 20%, at least about 30%, atleast about 40%, at least about 50%, or at least about 60%. In somecases, reducing or eliminating droplet entrainment may increase theamount of purified water recovered from bubble condenser 100 by anamount in the range of about 1% to about 10%, about 1% to about 20%,about 1% to about 40%, about 1% to about 60%, about 5% to about 20%,about 5% to about 40%, about 5% to about 60%, about 10% to about 20%,about 10% to about 30%, about 10% to about 40%, about 10% to about 50%,about 10% to about 60%, about 20% to about 30%, about 20% to about 40%,about 20% to about 50%, about 20% to about 60%, about 30% to about 40%,about 30% to about 50%, about 30% to about 60%, about 40% to about 50%,about 40% to about 60%, or about 50% to about 60%.

In some cases, stack 800 has a largest cross-sectional dimension (e.g.,length, diameter) D_(s) that is greater than the largest cross-sectionaldimension D_(o) of outlet 130. In certain embodiments, largestcross-sectional dimension D_(s) is at least about 0.01 m, at least about0.02 m, at least about 0.05 m, at least about 0.1 m, at least about 0.2m, at least about 0.5 m, at least about 1 m, at least about 2 m, or atleast about 5 m greater than the largest cross-sectional dimension D_(o)of outlet 130. In some embodiments, largest cross-sectional dimensionD_(s) is greater than largest cross-sectional dimension D_(o) by anamount in the range of about 0.01 m to about 0.05 m, about 0.01 m toabout 0.1 m, about 0.01 m to about 0.5 m, about 0.01 m to about 1 m,about 0.01 m to about 5 m, about 0.1 m to about 0.5 m, about 0.1 m toabout 1 m, about 0.1 m to about 5 m, about 0.5 m to about 1 m, about 0.5m to about 5 m, or about 1 m to about 5 m. Without wishing to be boundby a particular theory, increasing the largest cross-sectional dimensionof a conduit through which the dehumidified gas stream flows may reducethe velocity of the dehumidified gas stream. As a result, any liquiddroplets that may be present in the dehumidified gas stream may fall outof the dehumidified gas stream and return to liquid bath 150 instead ofexiting bubble column condenser 100 through outlet 130.

In some embodiments, the bubble column condenser comprises at least twostages for recovery of a condensable fluid from a gas or gas mixture.For example, the stages may be arranged such that a gas or gas mixtureflows sequentially from the first stage to the second stage. In somecases, the stages may be arranged in a vertical fashion, e.g., a firststage positioned below a second stage within the condenser. In somecases, the stages may be arranged in a horizontal fashion, e.g., a firststage positioned to the right of a second stage. The presence ofmultiple stages within a bubble column condenser may, in certain cases,advantageously lead to higher recovery of the condensable fluid inliquid phase. For example, the presence of multiple stages may providenumerous locations wherein the gas or gas mixture may be treated torecover the condensable fluid. That is, the gas or gas mixture maytravel through more than one liquid bath (e.g., liquid layer) in whichat least a portion of the gas or gas mixture undergoes condensation.Additionally, in some embodiments, the use of multiple stages canproduce a condenser liquid outlet stream having increased temperature(e.g., relative to the condenser liquid input stream), as described morefully below. This may be advantageous in systems where heat from thecondenser liquid outlet stream is transferred to a separate streamwithin the system, such as an evaporator/humidifier input stream. Insuch cases, the ability to produce a heated condenser liquid outletstream can increase energy effectiveness of the system. Additionally,use of multiple stages may also enable greater flexibility for fluidflow within the system. For example, extraction and/or injection offluids from intermediate bubble column stages may occur via intermediateexchange conduits.

FIG. 2A shows an exemplary cross-sectional diagram of a multi-stagebubble column condenser. In FIG. 2A, bubble column condenser 200comprises first stage 210 and second stage 220 arranged vertically abovefirst stage 210. First stage 210 includes chamber 212, liquid layer 214positioned within chamber 212, and first inlet 234 for a first gas orgas mixture comprising a condensable fluid in a vapor phase. First stage210 also includes a first vapor distribution region, which is locatedabove liquid layer 214 (e.g., the portion of chamber 212 that is notoccupied by liquid layer 214). Additionally, first stage 210 comprisesliquid outlet 216 for exit of a condensed liquid output stream fromcondenser 200. First inlet 234, which is in fluid communication with asource of the first gas or gas mixture, is also coupled to bubblegenerator 208 such that the first gas or gas mixture entering inlet 234is fed into bubble generator 208. The first gas or gas mixture may bedelivered to inlet 234 by pump 202 through conduit 204 from a source ofthe first gas or gas mixture fluidly connected to condenser 200. In someembodiments, first gas inlet 234 and/or bubble generator 208 occupy theentire bottom surface of first stage 210 or chamber 212. In otherembodiments, first gas inlet 234 and/or bubble generator 208 occupy asmaller portion of the bottom surface of first stage 210 or chamber 212.

Second stage 220 is in fluid communication with first stage 210 andincludes chamber 224, liquid layer 226 positioned within chamber 224,and bubble generator 222, which is arranged to receive the first gas orgas mixture from first stage 210. Second stage 220 also includes secondstage liquid inlet 232, which is in fluid communication with a source ofthe condensable fluid in liquid phase and delivers the condensable fluidto liquid layer 226. Additionally, second stage 220 comprises gas outlet230, through which a bubble column condenser gas outlet stream may exit.Second stage 220 also comprises a second vapor distribution regionlocated above liquid layer 226 (e.g., the portion of chamber 224 that isnot occupied by liquid layer 226).

Conduit/downcomer 218 is positioned between first stage 210 and secondstage 220, providing a path for any overflowing condensable fluid (e.g.,from liquid layer 226) to travel from second stage 220 to liquid layer214 in first stage 210. The maximum height of liquid layer 226 is set byweir 228, such that any additional condensable fluid of liquid layer 226above that maximum height flows through conduit/downcomer 218 to liquidlayer 214 in first stage 210. The outlet of conduit/downcomer 218 issubmerged in liquid layer 214, such the first gas or gas mixture flowingthrough first stage 210 is prevented from entering conduit/downcomer218. In some cases, first stage 210 further comprises optional weir 254.Optional weir 254 may establish a height of liquid surroundingconduit/downcomer 218 that is higher than the height of liquid layer 214in first stage 210. It has been recognized that it may be advantageousfor the height of liquid surrounding conduit/downcomer 218 to be higherthan the height of liquid layer 214, as such a configuration may resultin the hydrostatic head of liquid that the first gas or gas mixture hasto overcome being higher in the liquid around conduit/downcomer 218 thanin liquid layer 214. Such a configuration may thus prevent the first gasor gas mixture from flowing through conduit/downcomer 218 and therebybypassing bubble generator 222.

Optional vapor distribution chamber 206 may be positioned below firststage 210 and may allow the first gas or gas mixture to be distributedalong the bottom surface of bubble generator 208. Those of ordinaryskill in the art would be capable of selecting the appropriate systemconfiguration for use in a particular application.

In operation, a first gas or gas mixture (provided by a source of gasnot pictured in FIG. 2) containing a condensable fluid is pumped by pump202 through conduit 204 to optional vapor distribution chamber 206,where the first gas or gas mixture is substantially homogeneouslydistributed along the bottom surface of first stage 210 to first stagegas inlet 234 and bubble generator 208. As the first gas or gas mixturetravels through bubble generator 208, gas bubbles are formed. The gasbubbles travel through liquid layer 214, which is maintained at atemperature below that of the gas bubbles. The gas bubbles undergo acondensation process and transfer heat and/or mass of the condensablefluid to liquid layer 214. For example, the condensable fluid may bewater, such that the gas bubbles are at least partially dehumidified asthey travel through liquid layer 214. Bubbles of the at least partiallydehumidified gas then enter the first vapor distribution region. The atleast partially dehumidified gas may, in some cases, be substantiallyhomogenously distributed throughout the first vapor distribution region.The at least partially dehumidified gas then enters bubble generator222, where gas bubbles of the at least partially dehumidified gas areformed. Bubbles of the at least partially dehumidified gas then travelthrough liquid layer 226, which is maintained at a temperature belowthat of the gas bubbles, and heat and mass of the condensable fluid aretransferred to liquid layer 226. Bubbles of the further dehumidified gasthen enter the second vapor distribution region. The furtherdehumidified gas may, in some cases, be substantially homogeneouslydistributed throughout the second vapor distribution region. The furtherdehumidified gas then exits the bubble column condenser through secondstage outlet 230 as a bubble column condenser gas outlet stream.

In some embodiments, a stream of condensable fluid in liquid phase flowsin the opposite direction as (i.e., counterflow to) the gas or gasmixture. For example, condensable liquid can enter bubble columncondenser 200 through second stage liquid inlet 232, which is in fluidcommunication with a source of the condensable fluid in liquid phase.The condensable liquid is first delivered to liquid layer 226, which hasa maximum height specified by weir 228. If the height of liquid layer226 exceeds the maximum height, an amount of condensable liquid mayspill over the top of the weir through conduit/downcomer 218 to liquidlayer 214 and exit the condenser via condenser liquid outlet 216. Thetemperature of the condenser liquid outlet stream may be greater thanthat of the condensable liquid entering the condenser at second stageliquid inlet 232, as the condensable liquid is passed through variousstages within the condenser. In some cases, heat is transferred to thecondensable liquid at each of the stages within the bubble columncondenser. In some cases, as the number of stages through which thecondensable fluid passes increases, the temperature of the condenserliquid outlet stream increases. Such a configuration may be advantageousin systems where heat from the condenser liquid outlet stream istransferred to another component within the system. In some cases, theheat transfer may occur at a location within the system that is notwithin the condenser. For example, heat from the condenser liquid outletstream may be transferred to a humidifier input stream within ahumidifier and/or a heat exchanger in fluid communication with thecondenser.

As shown in FIG. 2B, bubble condenser 200 can further comprise anoptional second inlet 205. Optional second inlet 205 may be in fluidcommunication with a source of a second gas or gas mixture, and thesecond gas or gas mixture may be delivered to inlet 205 via optionalconduit 203. The second gas or gas mixture may comprise a condensablefluid in vapor phase. In certain cases, the condensable fluid may bewater. The second gas or gas mixture may, in some embodiments, furthercomprise one or more non-condensable gases (e.g., air).

In some embodiments, a bubble column condenser may comprise at least onevapor distribution region to allow for introduction of a vapor mixturethat contains a condensable fluid in vapor phase and/or anon-condensable gas (e.g., carrier gas). Typically, the vapordistribution region may be selected to have sufficient volume to allowvapors to substantially evenly diffuse over the cross section of thebubble column condenser. In some cases, the vapor distribution chambermay provide sufficient volume to allow entrained droplets from a liquidlayer in a stage to return to the liquid layer. In some cases, the vapordistribution region may be positioned at or near a bottom portion of thebubble column condenser. In some cases, the vapor distribution region ispositioned between two consecutive or adjacent bubble generatingchambers. For example, the vapor distribution region may keep the liquidlayers of the two consecutive or adjacent bubble generating chambersseparate, thereby increasing the thermodynamic effectiveness of thebubble column condenser. The vapor distribution region may include avapor inlet in fluid communication with a source of a vapor mixturecomprising a condensable fluid in vapor phase and/or a non-condensablegas. In some cases, the bubble column condenser includes more than onevapor distribution region.

In some embodiments, a vapor distribution chamber comprising a vapordistribution region may further comprise a liquid layer (e.g., a sumpvolume). For example, liquid may collect in the sump volume afterexiting the last stage of a bubble column condenser, prior to exitingthe bubble column condenser. In some embodiments, the sump volume may bein direct contact with a liquid outlet of the bubble column condenser.In certain cases, the sump volume may be in fluid communication with apump that pumps liquid out of the bubble column condenser. The sumpvolume may, for example, provide a positive suction pressure on theintake of the pump, and may advantageously prevent negative (e.g.,vacuum) suction pressure that may induce deleterious cavitation bubbles.In some cases, the sump volume may advantageously decrease thesensitivity of the bubble column condenser to sudden changes in heattransfer rates (e.g., due to intermittent feeding of salt-containingwater and/or intermittent discharge of pure water).

FIG. 2C provides an exemplary illustration of a bubble column condensercontaining a vapor distribution region positioned above an amount of acondensable fluid in liquid phase. In FIG. 2C, a bubble column condenser200 includes a vapor distribution chamber 244, a first stage 210, and asecond stage 220. Vapor distribution chamber 244, located at the bottomof condenser 200, includes a liquid layer 234, which may be in directcontact with a liquid outlet 242. Vapor distribution chamber 244 alsoincludes a vapor distribution region 236, which may be positioned aboveliquid layer 234 and may be in direct contact with a vapor inlet 240 influid communication with a source of a vapor mixture (e.g., a gas or gasmixture comprising a condensable liquid in a vapor phase). First stage210 includes a chamber 212, liquid layer 214 positioned within chamber212, bubble generator 208, and first liquid inlet 234 for the vapormixture. First stage 210 also includes a first vapor distribution regionlocated above liquid layer 214 (e.g., the portion of chamber 212 that isnot occupied by liquid layer 214). Second stage 220 includes a chamber224, a liquid layer 226 positioned within chamber 224, a bubblegenerator 222, a liquid inlet 232 for receiving a stream of thecondensable fluid in liquid phase (e.g., the liquid phase), and a vaporoutlet 230. Second stage 220 also includes a second vapor distributionregion positioned above liquid layer 226 (e.g., the portion of chamber224 that is not occupied by liquid layer 226).

In operation, a vapor mixture may enter vapor distribution region 236via vapor inlet 240. In vapor distribution region 236, the vapor mixturemay be substantially homogeneously distributed throughout vapordistribution region 236. The vapor mixture may then travel throughbubble generator 208, and gas bubbles may form and move through liquidlayer 214, which may be maintained at a temperature below that of thegas bubbles. As noted above, the gas bubbles may undergo a condensationprocess and transfer heat and/or mass of the condensable fluid to liquidlayer 214. Bubbles of the at least partially dehumidified vapor mixturemay enter the first vapor distribution region, and the at leastpartially dehumidified vapor mixture may be substantially homogeneouslydistributed throughout the first vapor distribution region. The at leastpartially dehumidified vapor mixture may then enter bubble generator 222and form gas bubbles, which may travel through liquid layer 226. Bubblesof the further dehumidified vapor mixture may then enter the secondvapor distribution region, and the further dehumidified vapor mixturemay be substantially homogeneously distributed throughout the secondvapor distribution region. The vapor mixture may then exit bubble columncondenser 200 through vapor outlet 230 as a bubble column condenser gasoutlet stream.

Again referring to FIG. 2C, a stream of a condensable fluid in liquidphase may enter second stage 220 via liquid inlet 232. The liquid phasemay first enter and be combined with liquid layer 226, which may have amaximum height specified by weir 228. The liquid phase may travellengthwise across the surface of bubble generator 222, in the directionof arrow 246. If the height of liquid layer 226 exceeds the height ofweir 228, excess liquid phase may flow over the top of weir 228 throughconduit/downcomer 218 to liquid layer 214. The liquid phase may thenflow across the surface of bubble generator 208 in the direction ofarrow 248. As shown in FIG. 2C, the direction of arrow 248 may beopposite that of arrow 246. If the height of liquid layer 214 exceedsthe height of weir 250, excess liquid phase may flow over the top ofweir 250 through conduit/downcomer 238 to liquid layer 234. The liquidphase may then travel across the bottom surface of bottom chamber 244 inthe direction of arrow 252 and exit the bubble column condenser vialiquid outlet 242. As shown in FIG. 2C, the direction of arrow 252 maybe opposite that of arrow 248.

Bubble condenser 200 may, in certain cases, further comprise additionalvapor inlets. For example, FIG. 2D shows an exemplary illustration of abubble column condenser 200 comprising a first vapor distribution region236, which includes a first vapor inlet 240, and a second vapordistribution region 212, which includes a second vapor inlet 205. Firstvapor inlet 240 may be in fluid communication with a source of a firstvapor mixture. Second vapor inlet 205 may be in fluid communication witha source of a second vapor mixture.

In some cases, the first and second gases or gas mixtures may havesubstantially the same composition. In some cases, the first and secondgases or gas mixtures may have different compositions. The first andsecond gases or gas mixtures may, in certain cases, have different vapor(e.g., water vapor) concentrations. In some embodiments, the first andsecond gases or gas mixtures may have substantially the same vaporconcentration. In some cases, the first and second gases or gas mixturesmay be maintained at different temperatures. The difference between thetemperature of the first and second gases or gas mixtures may, incertain embodiments, be at least about 1° C., at least about 5° C., atleast about 10° C., at least about 20° C., at least about 50° C., atleast about 100° C., at least about 150° C., or at least about 200° C.In certain cases, the first and second gases or gas mixtures may bemaintained at substantially the same temperature.

It should be understood that the bubble column condenser may have anynumber of stages. In some embodiments, the bubble column condenser mayhave at least one, at least two, at least three, at least four, at leastfive, at least six, at least seven, at least eight, at least nine, or atleast ten or more stages. In some embodiments, the bubble columncondenser may have no more than one, no more than two, no more thanthree, no more than four, no more than five, no more than six, no morethan seven, no more than eight, no more than nine, no more than tenstages. The stages may be vertically aligned, i.e., the stages may bearranged vertically within the bubble column condenser, as shown in FIG.2. In some cases, the stages may be arranged such that the bottomsurfaces of the individual chambers (or bubble generators) aresubstantially parallel to one another. In some cases, the stages may bearranged such that the bottom surface of the individual chambers (orbubble generators) are substantially non-parallel to one another. Insome embodiments, the stages may be positioned at an angle. The stagesmay be horizontally aligned, i.e., the stages may be arrangedhorizontally within the bubble column condenser. In some suchembodiments, at least one stage of the bubble condenser may comprise aliquid layer, a vapor distribution region, a bubble generator submergedin the liquid layer, and a gas outlet fluidly connected to a bubblegenerator of another stage (e.g., an adjacent stage).

In some cases, the condenser may be constructed as a modular system suchthat various components or regions of the system are removable and/orexchangeable. For example, the system may include an area that canaccommodate one or more stages, and can be readily configured to includea desired number of stages. FIG. 7B shows an illustrative embodimentwhere the system includes eight trays, allowing for a capacity for oneto eight stages. Each stage can be added or removed by simply slidingthe stage in and out of the system. In embodiments such as this, thenumber and distance between stages may be readily tailored to suit aparticular application.

The stages of the condenser may have any shape suitable for a particularapplication. In some embodiments, at least one stage of the condenserhas a cross sectional shape that is substantially circular,substantially elliptical, substantially square, substantiallyrectangular, and/or substantially triangular. In certain embodiments,each stage of the condenser has a cross sectional shape that issubstantially circular, substantially elliptical, substantially square,substantially rectangular, and/or substantially triangular. In somecases, the stages of the condenser have a relatively large aspect ratio.As used herein, the aspect ratio of an individual stage refers to theratio of the length of the individual stage to the width of theindividual stage. The length of an individual stage refers to thelargest internal cross-sectional dimension of the stage (e.g., in aplane perpendicular to a vertical axis of the stage). For example, inFIG. 1A, the length of stage 110 is indicated as L_(S). To furtherillustrate length, FIG. 1B provides an exemplary top-down view of stage110 (e.g., looking down on bubble generator 160). That is, FIG. 1B is anexemplary schematic illustration of a plane perpendicular to a verticalaxis of stage 110 (e.g., a cross-sectional plane). In FIG. 1B, thelength of stage 110 is indicated as L_(S). The width of an individualstage generally refers to the largest cross-sectional dimension of thestage (e.g., in a plane perpendicular to a vertical axis of the stage)measured perpendicular to the length. In FIG. 1B, the width of stage 110is indicated as W_(S).

In some embodiments, at least one stage has an aspect ratio of at leastabout 1.5, at least about 2, at least about 5, at least about 10, atleast about 15, or at least about 20. In some embodiments, at least onestage has an aspect ratio in the range of about 1.5 to about 5, about1.5 to about 10, about 1.5 to about 15, about 1.5 to about 20, about 2to about 5, about 2 to about 10, about 2 to about 15, about 2 to about20, about 5 to about 10, about 5 to about 15, about 5 to about 20, about10 to about 15, about 10 to about 20, or about 15 to about 20. In someembodiments, each stage of the condenser has an aspect ratio of at leastabout 1.5, at least about 2, at least about 5, at least about 10, atleast about 15, or at least about 20. In some embodiments, each stage ofthe condenser has an aspect ratio in the range of about 1.5 to about 5,about 1.5 to about 10, about 1.5 to about 15, about 1.5 to about 20,about 2 to about 5, about 2 to about 10, about 2 to about 15, about 2 toabout 20, about 5 to about 10, about 5 to about 15, about 5 to about 20,about 10 to about 15, about 10 to about 20, or about 15 to about 20.

In some embodiments, the height of the liquid layer within at least onestage of the bubble column condenser is relatively low duringsubstantially continuous operation. Generally, a water desalinationsystem is said to be operated substantially continuously when an aqueousstream is being fed to the desalination system at the same time that adesalinated product stream is being produced by the desalination system.The height of the liquid layer within a stage can be measured from thesurface of the bubble generator that contacts the liquid layer to thetop surface of the liquid layer. As noted herein, having a relativelylow level of liquid phase in at least one stage may, in someembodiments, advantageously result in a low pressure drop between theinlet and outlet of an individual stage. Without wishing to be bound bya particular theory, the pressure drop across a given stage of thecondenser may be due, at least in part, to the hydrostatic head of theliquid in the stage that the gas has to overcome. Therefore, the heightof the liquid layer in a stage may be advantageously kept low to reducethe pressure drop across that stage.

In some embodiments, during substantially continuous operation of thebubble column condenser, the liquid layer within at least one stage ofthe condenser has a height of (e.g., the height of condensable fluidwithin a stage is) less than about 0.1 m, less than about 0.09 m, lessthan about 0.08 m, less than about 0.07 m, less than about 0.06 m, lessthan about 0.05 m, less than about 0.04 m, less than about 0.03 m, lessthan about 0.02 m, less than about 0.01 m, or, in some cases, less thanabout 0.005 m. In some embodiments, during substantially continuousoperation of the bubble column condenser, the liquid layer within eachstage of the condenser has a height of less than about 0.1 m, less thanabout 0.09 m, less than about 0.08 m, less than about 0.07 m, less thanabout 0.06 m, less than about 0.05 m, less than about 0.04 m, less thanabout 0.03 m, less than about 0.02 m, less than about 0.01 m, or, insome cases, less than about 0.005 m.

In condensers described herein, the ratio of the height of the liquidlayer (e.g., water) in a stage of the condenser to the length of thestage of the condenser may be relatively low. The length of the stage ofthe condenser generally refers to the largest internal cross-sectionaldimension of the stage of the condenser. In some embodiments, the ratioof the height of the liquid layer within at least one stage of thebubble column condenser during steady-state operation to the length ofthe at least one stage of the condenser is less than about 1, less thanabout 0.8, less than about 0.6, less than about 0.4, less than about0.2, less than about 0.18, less than about 0.16, less than about 0.14,less than about 0.12, less than about 0.1, or, in some cases, less thanabout 0.05. In some embodiments, the ratio of the height of the liquidlayer within each stage of the bubble column condenser duringsteady-state operation to the length of each corresponding stage of thecondenser is less than about 1, less than about 0.8, less than about0.6, less than about 0.4, less than about 0.2, less than about 0.18,less than about 0.16, less than about 0.14, less than about 0.12, lessthan about 0.1, or, in some cases, less than about 0.05.

In some embodiments, the height of an individual stage within thecondenser (e.g., measured vertically from the bubble generatorpositioned at the bottom of the stage to the top of the chamber withinthe stage) may be relatively small. As noted above, reducing the heightof one or more stages of the condenser may potentially reduce costsand/or potentially increase heat and mass transfer within the system. Insome embodiments, the height of at least one stage is less than about0.5 m, less than about 0.4 m, less than about 0.3 m, less than about 0.2m, less than about 0.1 m, or, in some cases, less than about 0.05 m. Insome embodiments, the height of each stage is less than about 0.5 m,less than about 0.4 m, less than about 0.3 m, less than about 0.2 m,less than about 0.1 m, or, in some cases, less than about 0.05 m. Thetotal height of the condenser column may, in some embodiments, be lessthan about 10 m, less than about 8 m, less than about 6 m, less thanabout 4 m, less than about 2 m, less than about 1 m, or, in some cases,less than about 0.5 m.

In some embodiments, the pressure drop across a stage (i.e. thedifference between inlet gas pressure and outlet gas pressure) for atleast one stage in the bubble column condenser is less than about 2000Pa, less than about 1500 Pa, less than about 1000 Pa, less than about800 Pa, less than about 500 Pa, less than about 200 Pa, less than about100 Pa, or, in some cases, less than about 50 Pa. In some embodiments,the difference between bubble column condenser inlet gas pressure andbubble column condenser outlet gas pressure is less than about 2000 Pa,less than about 1500 Pa, less than about 1000 Pa, less than about 800Pa, less than about 500 Pa, less than about 200 Pa, less than about 100Pa, or, in some cases, less than about 50 Pa.

In some embodiments, the bubble column condenser may exhibit improvedheat transfer properties. For example, when the bubble column condenseris in substantially continuous operation, the heat transfer coefficientmay be at least about 2000 W/(m² K), at least about 3000 W/(m² K), atleast about 4000 W/(m² K), or, in some cases, at least about 5000 W/(m²K).

In some cases, the temperature of the condenser liquid inlet stream maybe different than the temperature of the condenser liquid outlet stream.For example, during substantially continuous operation of the bubblecolumn condenser, the temperature of the condenser liquid inlet streammay be less than about 100° C., less than about 90° C., less than about80° C., less than about 70° C., less than about 60° C., less than about50° C., less than about 45° C., less than about 40° C., less than about30° C., less than about 20° C., or, in some cases, less than about 10°C. In some cases, the temperature of the condenser liquid inlet streammay range from about 0° C. to about 100° C., from about 10° C. to about90° C., or from about 20° C. to about 80° C. During substantiallycontinuous operation of the bubble column condenser, the temperature ofthe condenser liquid outlet stream may be at least about 50° C., atleast about 60° C., at least about 70° C., at least about 80° C., atleast about 85° C., at least about 90° C., or at least about 100° C. Insome cases, the temperature of the condenser liquid outlet stream mayrange from about 50° C. to about 100° C., from about 60° C. to about 90°C., or from about 60° C. to about 85° C. The difference in inlet andoutlet liquid temperature may be at least about 5° C., at least about10° C., at least about 20° C., or, in some cases, at least about 30° C.In some cases, the difference in inlet and outlet temperature may rangefrom about 5° C. to about 30° C., from about 10° C. to about 30° C., orfrom about 20° C. to about 30° C.

In some embodiments, the gas or gas mixture may travel through thecondenser at a relatively high flow rate. It may be advantageous, incertain embodiments, for gas flow rate to be relatively high since heatand mass transfer coefficients are generally higher at higher gas flowrates. In some embodiments, the gas or gas mixture may have a flow rateof at least about 10 cubic foot per minute (cfm) per square foot (ft²),at least about 20 cfm/ft², at least about 40 cfm/ft², at least about 60cfm/ft², at least about 80 cfm/ft², at least about 100 cfm/ft², at leastabout 120 cfm/ft², at least about 140 cfm/ft², at least about 160cfm/ft², at least about 180 cfm/ft², or, in some cases, at least about200 cfm/ft². In some embodiments, the gas or gas mixture may have a flowrate in the range of about 10 cfm/ft² to about 200 cfm/ft², about 20cfm/ft² to about 200 cfm/ft², about 40 cfm/ft² to about 200 cfm/ft²,about 60 cfm/ft² to about 200 cfm/ft², about 80 cfm/ft² to about 200cfm/ft², about 100 cfm/ft² to about 200 cfm/ft², about 120 cfm/ft² toabout 200 cfm/ft², about 140 cfm/ft² to about 200 cfm/ft², about 160cfm/ft² to about 200 cfm/ft², or about 180 cfm/ft² to about 200 cfm/ft².

In some embodiments, the gas or gas mixture may contain a certain amountof water (e.g., may be “humidified”) such that, after flowing throughthe condenser, the gas or gas mixture may be substantially dehumidifiedrelative to the gas or gas mixture prior to flowing through thecondenser. At a given set of system conditions, the gas or gas mixturemay have a relative humidity. Relative humidity generally refers to theratio of the partial pressure of water vapor in a mixture of air andwater to the saturated vapor pressure of water at a given temperature.In some embodiments, the relative humidity of the gas or gas mixture atat least one gas inlet to the bubble column condenser may be at leastabout 70%, at least about 80%, at least about 90%, or about 100%. Insome embodiments, the relative humidity of the gas at a gas outlet tothe bubble column condenser may be less than about 20%, less than about10%, less than about 5%, or about 0%.

In some embodiments, the bubble column condenser comprises at least onebubble generator. Examples of types of bubble generators include sieveplates, spargers, and nozzle-type bubble generators. In someembodiments, a bubble generator may comprise a plurality of perforationsthrough which vapor can travel. The bubble generators may be operated atvarious bubble generator speeds, with various features (e.g., holes)used for generation of bubbles, or the like. The selection of bubblegenerator can affect the size and/or shape of the gas bubbles, therebyaffecting heat transfer from the gas bubbles to the condensable fluid ina liquid phase. Those of ordinary skill in the art are capable ofselecting the appropriate bubble generator and/or bubble generatorconditions in order to produce a particular desired set of gas bubbles.In some embodiments, the bubble generator comprises a sparger plate. Ithas been recognized that a sparger plate may have certain advantageouscharacteristics. For example, the pressure drop across a sparger platemay be low. Additionally, the simplicity of the sparger plate may renderit inexpensive to manufacture and/or resistant to the effects offouling. The sparger plate may, in some embodiments, comprise aplurality of holes. In some embodiments, at least a portion of theplurality of holes have a diameter (or smallest cross-sectionaldimension of a line passing through the geometric center of the hole fornon-circular holes) in the range of about 0.1 mm to about 50 mm, about0.1 mm to about 25 mm, about 0.1 mm to about 15 mm, or, in some cases,about 1 mm to about 15 mm. In some embodiments, at least a portion ofthe plurality of holes have a diameter of about 1 mm, about 2 mm, about3 mm, about 3.2 mm, or, in some cases, about 4 mm. In some cases, thesparger plate may be arranged along the bottom surface of an individualstage within the condenser. In some cases, the surface area of thesparger plate may be selected such that it covers at least approximately50%, at least approximately 60%, at least approximately 70%, at leastapproximately 80%, at least approximately 90%, or approximately 100% ofa cross-section of the condenser. In some embodiments, the bubblegenerator comprises one or more perforated pipes. The perforated pipes,which can extend from a central conduit, can feature, for example, aradial, annular, spider-web, or hub-and-spoke configuration throughwhich the gas or gas mixture is pumped from an external source. In someembodiments, at least one bubble generator may be coupled to the inletof a stage. In some embodiments, a bubble generator is coupled to theinlet of each stage of the bubble column condenser.

The condensers described herein may further include one or morecomponents positioned to facilitate, direct, or otherwise affect flow ofa fluid within the condenser. In some embodiments, at least one chamberof at least one stage of the bubble column condenser may include one ormore baffles positioned to direct flow of a fluid, such as a stream ofthe condensable fluid in liquid phase (e.g., water). In certain cases,each chamber of the bubble column condenser may comprise one or morebaffles. Suitable baffles for use in embodiments described hereininclude plate-like articles having, for example, substantiallyrectangular-shape, as shown by the illustrative embodiments in FIG. 6.Baffles may also be referred to as barriers, dams, or the like.

The baffle, or combination of baffles, may be arranged in variousconfigurations so as to direct the flow of a liquid within the chamber.In some cases, the baffle(s) can be arranged such that liquid travels ina substantially linear path from one end of the chamber to the other endof the chamber (e.g., along the length of a chamber having asubstantially rectangular cross-section). In some cases, the baffle(s)can be arranged such that liquid travels in a non-linear path across achamber, such a path having one or more bends or turns within thechamber. That is, the liquid may travel a distance within the chamberthat is longer than the length of the chamber. In some embodiments, oneor more baffles may be positioned along a bottom surface of at least onechamber within a bubble column condenser, thereby affecting the flow ofliquid that enters the chamber.

In some embodiments, a baffle may be positioned in a manner so as todirect flow of a liquid within a single chamber, e.g., along a bottomsurface of a chamber in either a linear or non-linear manner. In someembodiments, one or more baffles may be positioned substantiallyparallel to the transverse sides (i.e., width) of a chamber having asubstantially rectangular cross-sectional shape, i.e., may be atransverse baffle. In some embodiments, one or more baffles may bepositioned substantially parallel to the longitudinal sides (i.e.,length) of a chamber having a substantially rectangular cross-sectionalshape, i.e., may be a longitudinal baffle. In such configurations, oneor more longitudinal baffles may direct the flow of liquid along asubstantially non-linear path.

In some embodiments, one or more baffles may be positioned in a mannerso as to direct flow of a liquid within a single chamber along a paththat may promote efficiency of heat and/or mass transfer. For example, achamber may comprise a liquid entering through a liquid inlet at a firsttemperature and a gas or gas mixture entering through a bubble generatorat a second, different temperature. In certain cases, heat and masstransfer between the liquid and the gas or gas mixture may be increasedwhen the first temperature approaches the second temperature. One factorthat may affect the ability of the first temperature to approach thesecond temperature may be the amount of time the liquid spends flowingthrough the chamber.

In some cases, it may be advantageous for portions of the liquid flowingthrough the chamber to spend substantially equal amounts of time flowingthrough the chamber. For example, heat and mass transfer may undesirablybe reduced under conditions where a first portion of the liquid spends ashorter amount of time in the chamber and a second portion of the liquidspends a longer amount of time in the chamber. Under such conditions,the temperature of a mixture of the first portion and the second portionmay be further from the second temperature of the gas or gas mixturethan if both the first portion and the second portion had spent asubstantially equal amount of time in the chamber. Accordingly, in someembodiments, one or more baffles may be positioned in the chamber tofacilitate liquid flow such that portions of the liquid flowing throughthe chamber spend substantially equal amounts of time flowing throughthe chamber. For example, one or more baffles within the chamber mayspatially separate liquid located at the inlet (e.g., liquid likely tohave spent a shorter amount of time in the chamber) from liquid locatedat the outlet (e.g., liquid likely to have spent a longer amount of timein the chamber). In some cases, one or more baffles within the chambermay facilitate liquid flow along flow paths having substantially thesame length. For example, the one or more baffles may prevent a firstportion of liquid from travelling along a substantially shorter pathfrom the inlet of the chamber to the outlet of the chamber (e.g., alongthe width of a chamber having a rectangular cross section) and a secondportion of liquid from travelling along a substantially longer path fromthe inlet of the chamber to the outlet of the chamber (e.g., along thelength of a chamber having a rectangular cross section).

In some cases, it may be advantageous to increase the amount of time aliquid spends flowing through a chamber. Accordingly, in certainembodiments, one or more baffles may be positioned within a singlechamber to facilitate liquid flow along a flow path having a relativelyhigh aspect ratio (e.g., the ratio of the average length of the flowpath to the average width of the flow path). For example, in some cases,one or more baffles may be positioned such that liquid flowing throughthe chamber follows a flow path having an aspect ratio of at least about1.5, at least about 2, at least about 5, at least about 10, at leastabout 20, at least about 50, at least about 75, or at least about 100.

In some cases, the aspect ratio of a liquid flow path through a chambermay be larger than the aspect ratio of the chamber. In certain cases,the presence of baffles to increase the aspect ratio of a liquid flowpath may facilitate the use of an apparatus having a relatively lowaspect ratio (e.g., about 1), such as an apparatus having asubstantially circular cross section. For example, FIG. 12 shows anexemplary schematic illustration of a chamber 1200 having asubstantially circular cross section (e.g., bottom surface) and a spiralbaffle 1202. In operation, liquid may enter chamber 1200 through aliquid inlet (not shown) positioned at or near the center of thesubstantially circular cross section. The liquid may then flow alongspiral baffle 1202 and exit chamber 1200 through a liquid outlet (notshown) positioned at the upper edge of the substantially circular crosssection. While the substantially circular cross section of chamber 1200has an aspect ratio of about 1, the aspect ratio of the liquid flow pathis substantially greater than 1 (e.g., approximately 4.5). As anadditional example, FIG. 13 shows an exemplary schematic illustration ofa chamber 1300 having a substantially circular cross section (e.g.,bottom surface) and comprising a first baffle 1302 and a second baffle1304. In operation, liquid may enter chamber 1300 through a liquid inlet(not shown) located in the upper left portion of the substantiallycircular cross section. The liquid may first flow in the direction ofarrow 1306. The liquid may then flow around baffle 1302 and flow in theopposite direction, in the direction of arrow 1308. The liquid may thenflow around baffle 1304 and flow in the direction of arrow 1310 andsubsequently exit chamber 1300 through a liquid outlet (not shown)located in the lower right portion of the substantially circular crosssection. While the aspect ratio of the circular cross section of chamber1300 is about 1, the aspect ratio of the liquid flow path throughchamber 1300 is substantially greater than 1.

In some embodiments, one or more weirs may be positioned within thechamber in a manner so as to control or direct flow of a liquid betweentwo chambers. For example, a weir may be positioned adjacent orsurrounding a region of the chamber that receives a stream of liquid,for example, from a different chamber above the region. In some cases, aweir may be positioned adjacent or surrounding a region of the chamberwhere liquid may flow out of the chamber, for example, into a differentchamber below. In some cases, a weir may be positioned within a chamberso as to not contact one or more walls of the chamber. In some cases, aweir may be positioned within a chamber so as to contact one or morewalls of the chamber.

The one or more weirs may be selected to have a height that is less thanthe height of the chamber. In some embodiments, the height of the weirsmay determine the maximum height for a liquid phase or layer in thechamber. For example, if a liquid layer residing in a first chamberreaches a height that exceeds the height of a weir positioned along abottom surface of the chamber, then at least a portion of the excessliquid layer may flow over the weir. In some cases, the excess liquidmay flow into a second, adjacent chamber, e.g., a chamber positionedbelow the first chamber. In some embodiments, at least one weir in achamber may have a height of less than about 0.1 m, less than about 0.09m, less than about 0.08 m, less than about 0.07 m, less than about 0.06m, less than about 0.05 m, less than about 0.04 m, less than about 0.03m, less than about 0.02 m, less than about 0.01 m, or, in some cases,less than about 0.005 m. In some embodiments, each weir in a chamber mayhave a height of less than about 0.1 m, less than about 0.09 m, lessthan about 0.08 m, less than about 0.07 m, less than about 0.06 m, lessthan about 0.05 m, less than about 0.04 m, less than about 0.03 m, lessthan about 0.02 m, less than about 0.01 m, or, in some cases, less thanabout 0.005 m.

In some embodiments, one or more weirs may be positioned to promote theflow of a liquid across the length of the chamber in a substantiallylinear path. For example, the chamber may be selected to have across-sectional shape having a length that is greater than its width(e.g., a substantially rectangular cross-section), such that the weirspromote flow of liquid along the length of the chamber. In some cases,it may be desirable to promote such cross flow across a chamber tomaximize the interaction, and therefore heat and/or mass transfer,between the liquid phase and the vapor phase of a condensable fluid.

In one embodiment, a chamber may include a first weir and a second weirpositioned along the bottom surface of the chamber. The first and secondweirs may be positioned at opposite ends of the chamber lengthwise, suchthat a stream of condensable fluid in liquid phase may flow along thelength of the chamber from the first weir to the second weir. Oneexample of a bubble generator system having such a configuration isillustrated in FIG. 7H. In FIG. 7H, bubble generator 702 (which caninclude a plurality of perforations) includes a first weir 704positioned at one end of the bubble generator. Bubble generator 702further comprises second weir 706 and third weir 708, both of which arepositioned at the opposite end of the bubble generator as first baffle704. In operation, a liquid may be introduced to the bubble generatorand may flow to region 704 a surrounded by weir 704. As additionalliquid is introduced and the height of the liquid in region 704 aexceeds the height of weir 704, excess liquid may flow over the top ofweir 704 and flow across the surface of bubble generator 702 in thedirection of arrow 710 across bubble generator 702. If the height of theliquid then exceeds the height of weir 706 and/or 708, excess liquid mayflow over the top of weir 706 and/or weir 708 and flow to anotherportion of the apparatus. In some cases, excess liquid may flow to achamber positioned below bubble generator 702.

In some embodiments, a bubble column condenser may include a pluralityof chambers arranged in a vertical stack, and one or more weirs and/orbaffles may be positioned in one or more chambers such that a liquid canflow across the length of the chamber. In some cases, the chambers canbe arranged such that liquid flows in opposing directions for adjacentchambers. For example, a bubble column condenser may comprise a firstchamber and a second chamber, and one or more weirs and/or baffles maybe positioned in each of the first and second chambers such that astream of condensable fluid in liquid phase flows along the length ofthe first chamber in a first direction and along the length of thesecond chamber in a second, opposing direction. For example, FIG. 2Cillustrates a configuration in which a bubble column condenser 200comprises a vapor distribution chamber 244, a first stage 210 comprisinga chamber 212, and a second stage 220 comprising a chamber 224. A streamof a condensable fluid in liquid phase may enter condenser 200 throughliquid inlet 232, and the liquid stream may flow across second stage 220in the direction of arrow 246. In first stage 210 positioned verticallybelow second stage 220, excess liquid stream from second stage 200 mayenter first stage 10 and may flow across first stage 210 in thedirection of arrow 248, where the direction of arrow 248 is oppositethat of arrow 246. In vapor distribution chamber 244 positionedvertically below first stage 210, excess liquid stream from first stage210 may flow in the direction of arrow 252, where the direction of arrow252 is in substantially the opposite direction as arrow 248 andsubstantially the same direction as arrow 246.

In some embodiments, a first weir may be positioned adjacent an areathat receives a liquid stream (e.g., from a liquid inlet, or from aregion above the first weir). The first weir may be positioned at theopposite end, lengthwise, from a second weir positioned adjacent anoutlet or a down corner that may deliver excess liquid to another regionof the apparatus. In some embodiments, the first weir and the secondweir may be positioned at the same end of the first chamber.

Some embodiments involve the use of both weirs and baffles to directliquid flow within and between chambers. In some cases, the baffle maybe a longitudinal baffle. In some cases, the baffle may be a transversebaffle (e.g., a horizontal baffle). One such embodiment is illustratedin FIG. 6, where a longitudinal baffle 604, weir 606, and weir 608 arepositioned on a bubble generator 602. Weir 606 and weir 608 arepositioned at a first end of bubble generator 602. Longitudinal baffle604 extends along the length of bubble generator 602, from the first endof bubble generator 602 toward the second, opposing end of bubblegenerator 602. The length of longitudinal baffle 604 is less than thelength of the bubble generator, providing a gap between the end oflongitudinal baffle 604 and the second, opposing end of bubble generator602 for a liquid to flow.

When system 600 is in use, weir 606 may receive a stream of acondensable fluid in liquid phase. The liquid may reside within region606 a enclosed by weir 606. As additional liquid is introduced and theheight of the liquid in enclosed region 606 a exceeds the height of weir606, excess liquid may flow over the top of weir 606 and flow along thelength of bubble generator 602, in the direction of arrow 610 asdirected by longitudinal baffle 604. The liquid phase may then flowacross the width of the bubble generator 602 via the gap betweenlongitudinal baffle 604 and a transverse wall of the chamber. Liquid maythen flow along the length of bubble generator 602 in the direction ofarrow 612, which is opposite that of arrow 610. When the height of theliquid exceeds the height of weir 608, excess liquid may flow over thetop of weir 608 and into another portion of the apparatus. It should beunderstood that a chamber may include comprise more than onelongitudinal baffle. In some embodiments, at least one longitudinalbaffle, at least two longitudinal baffles, at least three longitudinalbaffles, at least four longitudinal baffles, at least five longitudinalbaffles, at least ten longitudinal baffles, or more, are arranged withinthe chamber. In some embodiments, the chamber includes 1-10 longitudinalbaffles, 1-5 longitudinal baffles, or, 1-3 longitudinal baffles.

In some cases, at least one transverse baffle, at least two transversebaffles, at least three transverse baffles, at least four transversebaffles, at least five transverse baffles, at least ten transversebaffles, or more, are arranged within the chamber. In some embodiments,the chamber includes 1-10 transverse baffles, 1-5 transverse baffles,or, 1-3 transverse baffles.

The bubble column condenser may have any shape suitable for a particularapplication. In some embodiments, the bubble column condenser may have across section that is substantially circular, substantially elliptical,substantially square, substantially rectangular, or substantiallytriangular. It has been recognized that it may be advantageous for abubble column condenser to have a substantially circular cross section.In some cases, a bubble column condenser having a substantially circularcross section (e.g., a substantially cylindrical bubble columncondenser) may be easier to manufacture than a bubble column condenserhaving a cross section of a different shape (e.g., a substantiallyrectangular cross section). For example, for a substantially cylindricalbubble column condenser having a certain diameter (e.g., about 0.6 m orless), prefabricated pipes and/or tubes may be used to form the walls ofthe bubble column. In addition, a substantially cylindrical bubblecolumn condenser may be manufactured from a sheet material (e.g.,stainless steel) by bending the sheet and welding a single seam. Incontrast, a bubble column condenser having a cross section of adifferent shape may have more than one welded seam (e.g., a bubblecolumn condenser having a substantially rectangular cross section mayhave four welded seams). Further, a bubble column condenser having asubstantially circular cross section may require less material tofabricate than a bubble column condenser having a cross section of adifferent shape (e.g., a substantially rectangular cross section). Incertain embodiments, the bubble column condenser has a substantiallyparallelepiped shape, a substantially rectangular prism shape, asubstantially cylindrical shape, and/or a substantially pyramidal shape.

The bubble column condenser may have any size suitable for a particularapplication. In some embodiments, the largest cross-sectional dimensionof the bubble column condenser may be less than about 10 m, less thanabout 5 m, less than about 2 m, less than about 1 m, less than about 0.5m, or less than about 0.1 m. In some cases, the largest cross-sectionaldimension of the bubble column condenser may range from about 10 m toabout 0.01 m, from about 5 m to about 0.5 m, or from about 5 m to about1 m.

The exterior of the bubble column condenser may comprise any suitablematerial. In certain embodiments, the bubble column condenser comprisesstainless steel, aluminum, and/or a plastic (e.g., polyvinyl chloride,polyethylene, polycarbonate). In some embodiments, it may beadvantageous to minimize heat loss from the bubble column condenser tothe environment. In some cases, the exterior of the condenser and/or theinterior of the condenser may comprise a thermally insulating material.For example, the condenser may be at least partially coated, covered, orwrapped with a thermally insulating material. Non-limiting examples ofsuitable thermally insulating materials include elastomeric foam,fiberglass, ceramic fiber mineral wool, glass mineral wool, phenolicfoam, polyisocyanurate, polystyrene and polyurethane.

While the features described above have been discussed in the context ofcondensing apparatuses such as bubble column condensers, all of thedescribed features (e.g., shape, aspect ratio, presence of weirs and/orbaffles, etc.) may also be applied to humidifying apparatuses, such asbubble column humidifiers. Use of a bubble column humidifier may, insome cases, be advantageous compared to use of other types ofhumidifiers (e.g., packed bed humidifiers) for many of the same reasonsthat use of a bubble column condenser may be advantageous compared toother types of condensers. For example, a bubble column humidifier maybe characterized by improved performance (e.g., higher rates of heatand/or mass transfer, higher thermodynamic effectiveness) and/or reducedfabrication and/or material costs (e.g., reduced dimensions) compared toother types of humidifiers.

In certain cases, a bubble column humidifier comprises a plurality ofstages (e.g., the bubble column humidifier is a multi-stage bubblecolumn humidifier). The stages may be arranged such that a gas stream(e.g., an air stream) flows sequentially through a first stage, a secondstage, a third stage, and so on. In some embodiments, each stagecomprises a liquid layer having a temperature, and the temperature ofthe liquid layer of a stage may be lower than the temperature ofsubsequent stages. For example, in a three-stage bubble columnhumidifier, the temperature of the liquid layer of the first stage(e.g., the bottommost stage in a vertically arranged bubble column) maybe lower than the temperature of the liquid layer of the second stage,which may be lower than the temperature of the liquid layer of the thirdstage (e.g., the topmost stage in a vertically arranged bubble column).Within each stage, heat and mass may be transferred from the liquidlayer to bubbles of the gas stream.

To illustrate the operation of a multi-stage bubble column humidifier,the operation of an exemplary embodiment of a multi-stage bubble columnhumidifier, as illustrated in FIG. 2A, is described. According to someembodiments, apparatus 200 of FIG. 2A is a multi-stage bubble columnhumidifier. Bubble column humidifier 200 comprises all of the componentspreviously discussed in the context of a bubble column condenser (e.g.,first stage 210 comprising liquid layer 214 and bubble generator 208,second stage 220 comprising liquid layer 226 and bubble generator 222).However, liquid layers 214 and 226 comprise salt-containing waterinstead of substantially pure condensable fluid in a liquid phase.Additionally, the temperature of the salt-containing water of liquidlayers 214 and 226 is higher than the temperature of a first gas or gasmixture flowing through bubble column humidifier 200.

In operation, a gas or gas mixture may travel through bubble generator208, thereby forming bubbles. As the gas or gas mixture bubblessubsequently travel through liquid layer 214, which is maintained at atemperature above that of the gas or gas mixture, heat and mass aretransferred from the salt-containing water of liquid layer 214 to thebubbles of the gas or gas mixture, thereby at least partiallyhumidifying the gas or gas mixture. The at least partially humidifiedgas or gas mixture may then travel through a first vapor distributionregion and enter bubble generator 222, forming bubbles of the at leastpartially humidified gas or gas mixture. Bubbles of the at leastpartially humidified gas or gas mixture may then travel through liquidlayer 226, which has a temperature higher than the temperature of liquidlayer 214, and heat and mass may be transferred from liquid layer 226 tothe bubbles of the at least partially humidified gas or gas mixture,further humidifying the gas or gas mixture.

The bubble column humidifier may comprise any suitable material (e.g., amaterial that is heat-resistant and corrosion-resistant). Non-limitingexamples of suitable materials include chlorinated polyvinyl chloride,polyethylene, fiberglass-reinforced plastic, titanium alloys, Hastelloys(e.g., corrosion-resistant nickel alloys), superalloys (e.g.,molybdenum-based superalloys), and/or epoxy-coated metals.

Some embodiments relate to systems comprising a bubble column condenseras described herein arranged to be in fluid communication with anexternal heat exchanger. In such embodiments, heat may be transferredfrom a condenser liquid outlet stream to a coolant stream flowingthrough the external heat exchanger. The system can be configured suchthat the cooled condenser liquid outlet stream can then be returned tothe bubble column condenser through an inlet and be re-used as a liquidto form liquid layers in the stage(s) of the condenser. In this manner,the temperature of the liquid layers within the bubble column condensercan be regulated such that, in each stage, the temperature of the liquidlayer is maintained at a temperature lower than the temperature of thegas or gas mixture. In some cases, arrangement of the heat exchanger ata location that is external to the condenser, rather than at a locationthat is within the condenser, can allow for use of condensers asdescribed herein (e.g., condensers having reduced dimensions and/orreduced levels of liquid baths, etc.). In some cases, the heat exchangermay transfer heat absorbed from the condenser liquid outlet stream toanother fluid.

FIG. 3A shows an exemplary embodiment of a system 300 including a bubblecolumn condenser 302 fluidly connected to an external heat exchanger 304via conduits 306 and 308. Heat exchanger 304 further includes a coolantduring operation. In operation, a condenser liquid outlet streamcontaining an amount of absorbed heat exits condenser 302 via conduit306 at a temperature T₁ and enters external heat exchanger 304. Heat istransferred from the condenser liquid outlet stream to the coolant,which is maintained at a temperature T₃ that is lower than temperatureT₁ of the condenser liquid outlet stream. The condenser liquid outletstream then exits heat exchanger 304 via conduit 308 at temperature T₂,where T₂ is less than T₁, and is returned to condenser 302 via conduit308.

Heat exchanger 304 may optionally transfer any absorbed heat from thecondenser liquid outlet stream to another fluid stream. For example, aheat exchanger inlet stream (e.g., a heat exchanger coolant stream) mayenter heat exchanger 304 via conduit 310 at temperature T₃. As the heatexchanger inlet stream passes through heat exchanger 304, it may absorbheat transferred from the condenser liquid outlet stream. The heatexchanger inlet stream may then exit heat exchanger 304 via conduit 312as a heat exchanger outlet stream at temperature T₄, where T₄ is greaterthan T₃. In some embodiments, the condenser liquid inlet stream flowingthrough conduit 308 and heat exchanger inlet stream flowing throughconduit 310 may be substantially the same. In other embodiments, thecondenser liquid inlet stream and the heat exchanger inlet stream may bedifferent. In some cases, the condenser liquid outlet stream flowingthrough heat exchanger 304 (e.g., the stream flowing through conduits306 and 308) and the heat exchanger coolant stream (e.g., the streamflowing through conduits 310 and 312) may flow in substantially paralleldirections through heat exchanger 304. In other embodiments (asillustrated), the condenser liquid outlet stream flowing through heatexchanger 304 and the heat exchanger coolant stream may flow insubstantially non-parallel (e.g., opposite) directions through heatexchanger 304.

Any heat exchanger known in the art may be used. Examples of suitableheat exchangers include, but are not limited to, plate and frame heatexchangers, shell and tube heat exchangers, tube and tube heatexchangers, plate heat exchangers, plate and shell heat exchangers, andthe like. In a particular embodiment, the heat exchanger is a plate andframe heat exchanger. The heat exchanger may be configured such that afirst fluid stream and a second fluid stream flow through the heatexchanger. In some cases, the first fluid stream and the second fluidstream may flow in substantially the same direction (e.g., parallelflow), substantially opposite directions (e.g., counter flow), orsubstantially perpendicular directions (e.g., cross flow). The firstfluid stream may comprise, in certain cases, a fluid stream that flowsthrough a condenser (e.g., a condenser liquid outlet stream). In someembodiments, the second fluid stream may comprise a coolant. The firstfluid stream and/or the second fluid stream may comprise a liquid. Insome embodiments, the heat exchanger may be a liquid-to-liquid heatexchanger. In some cases, more than two fluid streams may flow throughthe heat exchanger.

The coolant may be any fluid capable of absorbing and transferring heat.Typically, the coolant is a liquid. The coolant may, in someembodiments, include water. In certain cases, the coolant may includesalt-containing water. For example, in a humidification-dehumidificationsystem, the coolant stream in the heat exchanger may be used to preheatsalt-containing water prior to entry into a humidifier.

In some embodiments, the heat exchanger may exhibit relatively high heattransfer rates. In some embodiments, the heat exchanger may have a heattransfer coefficient of at least about 150 W/(m² K), at least about 200W/(m² K), at least about 500 W/(m² K), at least about 1000 W/(m² K), atleast about 2000 W/(m² K), at least about 3000 W/(m² K), at least about4000 W/(m² K), or, in some cases, at least about 5000 W/(m² K). In someembodiments, the heat exchanger may have a heat transfer coefficient inthe range of at least about 150 W/(m² K) to at least about 5000 W/(m²K), at least about 200 W/(m² K) to about 5000 W/(m² K), at least about500 W/(m² K) to about 5000 W/(m² K), at least about 1000 W/(m² K) toabout 5000 W/(m² K), at least about 2000 W/(m² K) to about 5000 W/(m²K), at least about 3000 W/(m² K) to about 5000 W/(m² K), or at leastabout 4000 W/(m² K) to about 5000 W/(m² K).

In some embodiments, the heat exchanger may lower the temperature of thecondenser liquid outlet stream and/or other fluids flowing through theheat exchanger. For example, the difference between the temperature of afluid entering the heat exchanger in conduit 306 or 310 and the fluidexiting the heat exchanger via conduit 308 or 312, respectively, may beat least about 5° C., at least about 10° C., at least about 15° C., atleast about 20° C., at least about 30° C., at least about 40° C., atleast about 50° C., at least about 60° C., at least about 70° C., atleast about 80° C., at least about 90° C., at least about 100° C., atleast about 150° C., or, in some cases, at least about 200° C. In someembodiments, the difference between the temperature of a fluid enteringthe heat exchanger and the fluid exiting the heat exchanger may be inthe range of about 5° C. to about 30° C., about 5° C. to about 60° C.,about 5° C. to about 90° C., about 10° C. to about 30° C., about 10° C.to about 60° C., about 10° C. to about 90° C., about 20° C. to about 60°C., about 20° C. to about 90° C., about 20° C. to about 200° C., about30° C. to about 60° C., about 30° C. to about 90° C., about 40° C. toabout 200° C., about 60° C. to about 90° C., about 60° C. to about 200°C., about 80° C. to about 200° C., about 100° C. to about 200° C., orabout 150° C. to about 200° C.

In some embodiments, an optional external heating device may be arrangedin fluid communication with the bubble column condenser and/or theexternal heat exchanger. In certain cases, the heating device may bearranged such that, in operation, a condenser liquid outlet stream isheated in the heating device prior to entering the heat exchanger. Suchan arrangement may advantageously increase the amount of heattransferred from the condenser liquid outlet stream to another fluidstream flowing through the heat exchanger. For example, in ahumidification-dehumidification system, heat may be transferred from thecondenser liquid outlet stream to a salt-containing water stream (e.g.,a brine stream) prior to entry of the salt-containing water stream intoa humidifier.

The heating device may be any device that is capable of transferringheat to a fluid stream (e.g., a condenser liquid outlet stream). In somecases, the heating device is a heat exchanger. Any heat exchanger knownin the art may be used. Examples of suitable heat exchangers include,but are not limited to, plate and frame heat exchangers, shell and tubeheat exchangers, tube and tube heat exchangers, plate heat exchangers,plate and shell heat exchangers, and the like. In a particularembodiment, the heat exchanger is a plate and frame heat exchanger. Theheat exchanger may be configured such that a first fluid stream and asecond fluid stream flow through the heat exchanger. In some cases, thefirst fluid stream and the second fluid stream may flow in substantiallythe same direction (e.g., parallel flow), substantially oppositedirections (e.g., counter flow), or substantially perpendiculardirections (e.g., cross flow). The first fluid stream and/or the secondfluid stream may comprise a liquid. In some embodiments, the second heatexchanger is a liquid-to-liquid heat exchanger. The first fluid streammay, in some cases, comprise a fluid stream that flows through acondenser (e.g., a condenser liquid outlet stream). The second fluidstream may, in some cases, comprise a heating fluid. The second fluidstream may, in some cases, comprise a heating fluid. The heating fluidmay be any fluid capable of absorbing and transferring heat. In someembodiments, the heating fluid comprises water. In certain cases, theheating fluid comprises hot, pressurized water. In certain embodiments,heat may be transferred from the second fluid stream (e.g., the heatingfluid) to the first stream (e.g., the condenser liquid outlet stream) inthe heat exchanger. In some cases, more than two fluid streams may flowthrough the heat exchanger.

In some embodiments, the heating device is a heat collection device. Theheat collection device may be configured to store and/or utilize thermalenergy (e.g., in the form of combustion of natural gas, solar energy,waste heat from a power plant, or waste heat from combusted exhaust). Incertain cases, the heating device is configured to convert electricalenergy to thermal energy. For example, the heating device may be anelectric heater.

The heating device may, in some cases, increase the temperature of thecondenser liquid outlet stream and/or other fluid streams flowingthrough the heating device. For example, the difference between thetemperature of a fluid entering the heating device and the fluid exitingthe heating device may be at least about 5° C., at least about 10° C.,at least about 15° C., at least about 20° C., at least about 30° C., atleast about 40° C., at least about 50° C., at least about 60° C., atleast about 70° C., at least about 80° C., or, in some cases, at leastabout 90° C. In some embodiments, the difference between the temperatureof a fluid entering the heating device and the fluid exiting the heatexchanger may be in the range of about 5° C. to about 30° C., about 5°C. to about 60° C., about 5° C. to about 90° C., about 10° C. to about30° C., about 10° C. to about 60° C., about 10° C. to about 90° C.,about 20° C. to about 60° C., about 20° C. to about 90° C., about 30° C.to about 60° C., about 30° C. to about 90° C., or about 60° C. to about90° C. In some cases, the temperature of a fluid stream (e.g., thecondenser liquid outlet stream) being heated in the heating deviceremains below the boiling point of the fluid stream.

In some embodiments, an optional external cooling device may be arrangedin fluid communication with the bubble column condenser and/or theexternal heat exchanger. In certain cases, the cooling device may bearranged such that, in operation, a heat exchanger outlet stream (e.g.,a cooled condenser liquid outlet stream) is cooled in the cooling deviceprior to returning to the bubble column condenser.

A cooling device generally refers to any device that is capable ofremoving heat from a fluid stream (e.g., a liquid stream, a gas stream).In some embodiments, the cooling device is a heat exchanger. The heatexchanger may be configured such that a first fluid stream and a secondfluid stream flow through the heat exchanger. In some cases, the firstfluid stream and the second fluid stream may flow in substantially thesame direction (e.g., parallel flow), substantially opposite directions(e.g., counter flow), or substantially perpendicular directions (e.g.,cross flow). In some cases, heat is transferred from a first fluidstream to a second fluid stream. In certain embodiments, the coolingdevice is a liquid-to-gas heat exchanger. The first fluid stream may, incertain cases, comprise a fluid stream that is part of a loop ofcondenser liquid flowing between a condenser and a heat exchanger (e.g.,a condenser liquid outlet stream). The second fluid stream may, in somecases, comprise a coolant. The coolant may be any fluid capable ofabsorbing or transferring heat. In some embodiments, the coolantcomprises a gas. The gas may, in some cases, comprise air (e.g., ambientair). Heat exchangers that comprise air as a coolant may generally bereferred to as air-cooled heat exchangers. In some cases, more than twofluid streams flow through the cooling device. It should also be notedthat the cooling device may, in some embodiments, be a dry cooler, achiller, a radiator, or any other device capable of removing heat from afluid stream.

The cooling device may, in some cases, decrease the temperature of aheat exchanger outlet stream. In some embodiments, the cooling devicedecreases the temperature of the heat exchanger outlet stream by atleast about 5° C., at least about 10° C., at least about 15° C., atleast about 20° C., at least about 30° C., at least about 40° C., atleast about 50° C., at least about 60° C., at least about 70° C., atleast about 80° C., or, in some cases, at least about 90° C. In someembodiments, the cooling device decreases the temperature of the heatexchanger outlet stream by an amount in the range of about 5° C. toabout 30° C., about 5° C. to about 60° C., about 5° C. to about 90° C.,about 10° C. to about 30° C., about 10° C. to about 60° C., about 10° C.to about 90° C., about 20° C. to about 30° C., about 20° C. to about 60°C., about 20° C. to about 90° C., about 30° C. to about 60° C., about30° C. to about 90° C., or about 60° C. to about 90° C.

FIG. 3B shows an exemplary embodiment of a system 300 comprising abubble column condenser 302, an external heat exchanger 304, an externalheating device 314, and an external cooling device 316, each in fluidcommunication with one another. Heating device 314 is arranged to be influid communication with condenser 302 via liquid conduit 306. Heatingdevice 314 is also arranged to be in fluid communication with heatexchanger 304 via liquid conduit 318. In addition to being in fluidcommunication with heating device 314, heat exchanger 304 is arranged tobe in fluid communication with cooling device 316 via liquid conduit320. Cooling device 316 is arranged to be in fluid communication withcondenser 302 via liquid conduit 308.

In operation, in an exemplary embodiment, a condenser liquid outletstream exits condenser 302 via conduit 306 at a temperature T₁ andenters heating device 314. Heat is transferred to the condenser liquidoutlet stream as it flows through heating device 314. The condenserliquid outlet stream exits heating device 314 as a heating device outletstream (e.g., a heated condenser liquid outlet stream) at a temperatureT₂ that is higher than T₁. The heating device outlet stream then flowsthrough conduit 318 to heat exchanger 304. In heat exchanger 304, heatis transferred from the heating device outlet stream to another fluidstream (e.g., a salt-containing water stream) flowing through heatexchanger 304 via conduits 310 and 312. The heating device outlet streamexits heat exchanger 304 as a heat exchanger outlet stream at atemperature T₃ that is lower than T₂. The heat exchanger outlet streamthen flows through liquid conduit to cooling device 316. In someembodiments, as the heat exchanger outlet stream flows through coolingdevice 316, heat from the heat exchanger outlet stream is transferred toanother fluid stream (e.g., an air stream) flowing through coolingdevice 316 via conduits 322 and 324. The heat exchanger outlet streamthen exits cooling device 316 as a cooling device outlet stream at atemperature T₄ that is lower than T₃. The cooling device outlet streamat temperature T₄ then returns to condenser 302 via conduit 308.

In some embodiments, the bubble column condenser may be used in adesalination system. In some embodiments, the desalination system may bea humidification-dehumidification (HDH) system. In such systems, acondenser (e.g., bubble column condenser) may act as a dehumidifier tocondense substantially purified water from a humidified gas stream. Useof a bubble column condenser as a dehumidifier in an HDH system may beadvantageous because direct contact condensers, such as bubble columncondensers, may exhibit relatively higher heat transfer effectivenessthan other types of condensers, such as surface condensers. In someembodiments, the HDH system comprises a heat exchanger. In certaincases, the heat exchanger facilitates the transfer of heat from a fluidstream flowing through a condenser (e.g., a condenser liquid outletstream) to a fluid stream flowing through a humidifier (e.g., ahumidifier liquid inlet stream). For example, the heat exchanger mayadvantageously allow energy to be recovered from a condenser liquidoutlet stream and used to pre-heat a humidifier liquid inlet stream(e.g., a salt-containing water stream) prior to entry of the humidifierliquid inlet stream into the humidifier of the HDH system. This may, forexample, avoid the need for an additional heating device to heat thesalt-containing water stream. Alternatively, if a heating device isused, the presence of a heat exchanger to recover energy from acondenser liquid outlet stream may reduce the amount of heat required tobe applied to the salt-containing water stream. In some embodiments, theheat exchanger is an external heat exchanger. As noted above, the use ofan external heat exchanger may advantageously allow the use of bubblecolumn condensers as described herein (e.g., condensers having reduceddimensions and/or reduced levels of liquid baths, etc.). In someembodiments, the heat exchanger is an internal heat exchanger. Forexample, the internal heat exchanger may comprise a tube coil locatedwithin a bubble column condenser. The tube coil may be positioned suchthat at least a portion of the tube coil is in thermal contact with aliquid layer within a stage of the bubble column condenser. In amulti-stage bubble condenser comprising a plurality of stages, eachstage comprising a liquid layer, the tube coil may be positioned suchthat each liquid layer is in thermal contact with at least a portion ofthe tube coil. In some cases, a coolant (e.g., a salt-containing waterstream) may flow through the internal heat exchanger (e.g., the tubecoil), and heat may be transferred from the liquid layer(s) of thebubble column condenser to the coolant.

Other examples of HDH systems are described in U.S. Pat. No. 8,292,272,by Elsharqawy et al., filed Sep. 4, 2009, entitled “Water SeparationUnder Reduced Pressure”; U.S. Pat. No. 8,465,006, by Elsharqawy et al.,filed Sep. 21, 2012, entitled “Separation of a Vaporizable ComponentUnder Reduced Pressure”; U.S. Pat. No. 8,252,092, by Govindan et al.,filed Oct. 5, 2009, entitled “Water Separation Under Varied Pressure”;U.S. Pat. No. 8,496,234, by Govindan et al., filed Jul. 16, 2012,entitled “Thermodynamic Balancing of Combined Heat and Mass ExchangeDevices”; U.S. Patent Publication No. 2013/0074694, by Govindan et al.,filed Sep. 23, 2011, entitled “Bubble-Column Vapor Mixture Condenser”;U.S. Patent Publication No. 2013/0075940, by Govindan et al., filed Jul.12, 2012 as U.S. patent application Ser. No. 13/548,166, entitled“Bubble-Column Vapor Mixture Condenser”; and U.S. patent applicationSer. No. 13/916,038, by Govindan et al., filed Jun. 12, 2013, entitled“Multi-Stage Bubble Column Humidifier,” the contents of which areincorporated herein by reference in their entireties for all purposes.

An exemplary embodiment of an HDH system is shown in FIG. 4A. System 400includes a humidifier 402, a dehumidifier 404, a heat exchanger 406, areservoir of salt-containing water 408, and a reservoir of purifiedwater 410. Humidifier 402 and dehumidifier 404 are arranged in fluidcommunication via gas conduits 420 and 422. In some embodiments, system400 is a closed loop system, with a carrier gas stream circulatingbetween humidifier 402 and dehumidifier 404. In some cases, the carriergas stream may comprise a non-condensable gas. In addition to thecarrier gas stream, various liquid streams are circulated through system400. In one case, the stream may include salt-containing water, such asseawater, brackish water, saline water, brine, and/or industrialwastewater. In system 400, a reservoir of salt-containing water 408 isarranged in fluid communication with heat exchanger 406 via liquidconduit 412 and with humidifier 402 through liquid conduit 418.Humidifier 402 is also arranged to be in fluid communication with heatexchanger 406 via liquid conduits 414 and 416. In some embodiments,humidifier 402 may comprise a humidifier liquid inlet and outlet and ahumidifier gas inlet and outlet. In some cases, the humidifier isconfigured such that the liquid inlet is positioned at a first end(e.g., top end) of the humidifier, and the gas inlet is positioned at asecond, opposite end (e.g., bottom end) of the humidifier. Such aconfiguration may advantageously result in high thermal efficiency. Insome embodiments, the humidifier is configured to bring a carrier gasstream (e.g., dry air) into direct contact with a salt-containing waterstream, thereby producing a vapor-containing humidifier gas outletstream enriched in water relative to the gas received from thehumidifier gas inlet. Humidifier 402 may also produce a humidifierliquid outlet stream, a portion of which is returned to reservoir 408and a portion of which is flowed through heat exchanger 406 to be heatedand reintroduced to the humidifier. Any humidifier known to those ofordinary skill in the art may be utilized in the context of theembodiments described herein. According to certain embodiments, thehumidifier may be a packed bed humidifier. For example, in some suchembodiments, humidification of the carrier gas may be achieved byspraying salt-containing water from one or more nozzles located at thetop of the humidifier through a packing material (e.g., a polyvinylchloride packing material or a glass-filled polypropylene packingmaterial) while the carrier gas travels through the humidificationchamber and is brought into contact with the salt-containing water. Insome embodiments, the packing material may increase the surface area ofthe salt-containing water stream that is contact with the carrier gas,thereby increasing the portion of water that is vaporized into thecarrier gas. In some embodiments, the humidifier may be a bubble columnhumidifier. It has been recognized that use of a bubble columnhumidifier may, in some cases, be preferable to use of other types ofbubble column humidifiers (e.g., packed bed humidifiers). For example,bubble column humidifiers may be characterized by improved performance(e.g., higher rates of heat and/or mass transfer, higher thermodynamiceffectiveness) and/or reduced fabrication and/or material costs (e.g.,reduced dimensions).

In some embodiments, dehumidifier 404 is a bubble column condenser asdescribed herein. In some embodiments, condenser 404 is in fluidcommunication with reservoir 410 through conduit 430. Condenser 404 mayalso be in fluid communication with heat exchanger 406 via conduits 426and 428. Heat exchanger 406 may be any heat exchanger known in the art,as described elsewhere herein. In some embodiments the heat exchanger isconfigured such that a first fluid stream and a second fluid stream flowthrough the heat exchanger in substantially opposite direction (e.g.,counter flow). For example, FIG. 4B shows heat exchanger 406 as acounter flow device. The heat exchanger may, alternatively, be aparallel flow device and may be configured such that a first fluidstream and a second fluid stream flow in substantially the samedirection. FIG. 4A shows heat exchanger 406 as a parallel flow device.In some embodiments, the heat exchanger is a cross flow device, and theheat exchanger is configured such that a first fluid stream and a secondfluid stream flow in substantially perpendicular directions. In somecases, the heat exchanger is a liquid-to-liquid heat exchanger. In anexemplary embodiment, the heat exchanger is a plate and frame heatexchanger. In certain embodiments, heat exchanger 406 is in fluidcommunication with reservoir 410 via optional conduit 424. In operation,in the exemplary embodiment shown in FIG. 4A, a salt-containing waterstream flows from reservoir 408 to heat exchanger 406 via conduit 412 tobe heated prior to entering humidifier 402 (e.g., “preheated”). Thepreheated salt-containing water stream then travels from heat exchanger406 through conduit 414 to humidifier 402. In some cases, a firstportion of the preheated salt-containing water stream flows from heatexchanger 406 to humidifier 402, and, optionally, a second portion ofthe preheated salt-containing water stream is discharged from the systemand/or routed to another portion of the system. Separately, and in adirection that is opposite to the direction of flow for the preheatedsalt-containing water stream, a carrier gas stream provided by condenser404 is flowed through humidifier 402. In humidifier 402, the carrier gasstream, which is at a temperature that is lower than the preheatedsalt-containing water stream, is heated and humidified by the preheatedsalt-containing water stream. The humidified carrier gas stream exitshumidifier 402 and flows through gas conduit 420 to dehumidifier 404. Aportion of the salt-containing water stream returns to reservoir 408 viaconduit 418, and a portion flows through liquid conduit 416 to heatexchanger 406 to be preheated before being returned to humidifier 402via liquid conduit 414.

The humidified carrier gas stream is then flowed through bubble columncondenser 404. Flowing countercurrent to the humidified carrier gasstream in the bubble column condenser is a condenser liquid stream thatflows from heat exchanger 406 to bubble column condenser 404 throughconduit 426. In some embodiments, the condenser liquid stream comprisespurified water, which may be substantially pure water. In some cases, afirst portion of the condenser liquid stream that has flowed throughheat exchanger 406 is flowed to bubble column condenser 404 and,optionally, a second portion of the condenser liquid stream that hasflowed through heat exchanger 406 is discharged from the system and/orrouted to another portion of the system. In some cases in which aportion of the condenser liquid stream is discharged from the system,the rate that the liquid stream is discharged is about the same as therate that the liquid is being condensed, in order to maintain a constantvolume of water in the system. In bubble column condenser 404, thehumidified carrier gas stream undergoes a condensation process asdescribed elsewhere herein, wherein heat and mass are transferred fromthe humidified carrier gas stream to the condenser liquid stream,producing a dehumidified carrier gas stream and a condenser liquidoutlet stream. The dehumidified gas stream is returned to humidifier 402via gas conduit 422 for use as described herein. In some embodiments, aportion of the condenser liquid outlet stream is flowed through liquidconduit 430 to reservoir 410. The purified water that is collected inreservoir 410 can be used, for example, for drinking, watering crops,washing/cleaning, cooking, for industrial use, etc. The remainingportion of the condenser liquid outlet stream that is not flowed toreservoir 410 is returned to heat exchanger 406 via liquid conduit 428.As described herein, heat from the condenser liquid outlet stream may betransferred to the salt-containing water stream flowing through liquidconduits 412, 414, and 416. After flowing through heat exchanger 406,the condenser liquid outlet stream then flows through liquid conduit 426and returns to condenser 404 for reuse.

In some embodiments, an HDH system optionally comprises one or moreheating devices. An exemplary embodiment of an HDH system comprising twoheating devices is shown in FIG. 4C. In FIG. 4C, first heating device432 is arranged to be in fluid communication with heat exchanger 406 vialiquid conduit 436 and in fluid communication with humidifier 402 vialiquid conduit 414. Second heating device 434 is arranged to be in fluidcommunication with heat exchanger 406 via liquid conduit 438 andcondenser 404 via liquid conduit 428. The first heating device andsecond heating device may be any device that is capable of transferringheat to a fluid stream. In some embodiments, the first and/or secondheating device is a heat exchanger. The heat exchanger may be any heatexchanger known in the art, as described elsewhere herein (e.g., a plateand frame heat exchanger). In some embodiments, the first and/or secondheating device is a heat collection device. In some cases, the heatcollection device may be configured to store and/or utilize thermalenergy (e.g., in the form of combustion of natural gas, solar energy,waste heat from a power plant, or waste heat from combusted exhaust). Incertain cases, the heating device is configured to convert electricalenergy to thermal energy (e.g., an electric heater).

The first and/or second heating device may, in some cases, increase thetemperature of a fluid stream flowing through the first and/or secondheating device. For example, the difference between the temperature of afluid stream entering the first and/or second heating device and thefluid stream exiting the first and/or second heating device may be atleast about 5° C., at least about 10° C., at least about 15° C., atleast about 20° C., at least about 30° C., at least about 40° C., atleast about 50° C., at least about 60° C., at least about 70° C., atleast about 80° C., or, in some cases, at least about 90° C. In someembodiments, the difference between the temperature of a fluid streamentering the first and/or second heating device and the fluid streamexiting the first and/or second heating device may be in the range ofabout 5° C. to about 30° C., about 5° C. to about 60° C., about 5° C. toabout 90° C., about 10° C. to about 30° C., about 10° C. to about 60°C., about 10° C. to about 90° C., about 20° C. to about 60° C., about20° C. to about 90° C., about 30° C. to about 60° C., about 30° C. toabout 90° C., or about 60° C. to about 90° C.

In operation, a salt-containing water stream may first flow through heatexchanger 406. In heat exchanger 406, heat may be transferred fromanother fluid stream (e.g., a condenser liquid stream) to thesalt-containing water stream, resulting in a heated salt-containingwater stream. The heated salt-containing water stream may then be flowedthrough liquid conduit 436 to first heating device 432 to be heated,resulting in a further heated salt-containing water stream. The furtherheated salt-containing water stream may then be flowed to humidifier402.

In the opposite direction, a condenser liquid stream exitingdehumidifier 404 may flow through liquid conduit 428 to second heatingdevice 434 to be heated, resulting in a heated condenser liquid stream.The heated condenser liquid stream may then be directed to flow throughliquid conduit 438 to heat exchanger 406, and heat may be transferredfrom the heated condenser liquid stream to the salt-containing waterstream, resulting in a chilled condenser liquid stream. The chilledcondenser liquid stream may then be returned to condenser 404 throughliquid conduit 426.

It should be noted that although FIG. 4C shows a first heating deviceand a second heating device, the first and second heating devices mayindependently be present or absent in an HDH system. In someembodiments, a first heating device further heats a salt-containingwater stream after the stream has flowed through a heat exchanger. Insome embodiments, a second heating device heats a condenser liquidstream prior to the stream flowing through the heat exchanger. In somecases, the first heating device heats the salt-containing water streamand the second heating device heats the condenser liquid stream. In someembodiments, a single heating device may function as the first heatingdevice and second heating device and heat both the salt-containing waterstream and the condenser liquid stream. Further, there may be any numberof heating devices present in HDH system 400.

The humidifier may, in some cases, be substantially thermally separatedfrom the bubble column condenser. As used herein, substantial thermalseparation generally refers to a configuration such that there is littleto no direct conductive heat transfer between the humidifier and thebubble column condenser, for example through a shared heat transferwall. However, it should be understood that such a configuration doesnot preclude a mass flow carrying thermal energy (via gas and/or liquidflow) between the humidifier and the condenser.

Those of ordinary skill in the art would be able to select theappropriate conditions under which to operate the HDH systems describedherein for desired performance given the teaching and guidance of thepresent specification combined with the knowledge and skill of theperson of ordinary skill in the art. In some embodiments, the pressurein the humidification and/or dehumidification chamber is approximatelyambient atmospheric pressure. According to certain embodiments, thepressure in the humidification and/or dehumidification chamber is lessthan about 90,000 Pa. It may be desirable, in some embodiments, for thepressure in the humidifier to be less than approximately ambientatmospheric pressure. In some cases, as the pressure inside thehumidifier decreases, the ability of the humidified carrier gas to carrymore water vapor increases, allowing for increased production ofsubstantially pure water when the carrier gas is dehumidified in thecondenser. Without wishing to be bound by a particular theory, thiseffect may be explained by the humidity ratio, which generally refers tothe ratio of water vapor mass to dry air mass in moist air, being higherat pressures lower than atmospheric pressure. Those of ordinary skill inthe art would be able to select appropriate temperature and flow rateconditions for the HDH system components. In some embodiments, theselected conditions may be within the ranges described herein for thebubble column condenser.

According to some embodiments, a portion of the gas flow is extractedfrom at least one intermediate location in the humidifier and injectedinto at least one intermediate location in the bubble column condenser.Because the portion of the gas flow exiting the humidifier at anintermediate outlet (e.g., the extracted portion) has not passed throughthe entire humidifier, the temperature of the gas flow at theintermediate outlet may be lower than the temperature of the gas flow atthe main gas outlet of the humidifier. The location of the extractionpoints (e.g., outlets) and/or injection points (e.g., inlets) may beselected to increase the thermal efficiency of the system. For example,because a gas (e.g., air) may have increased vapor content at highertemperatures than at lower temperatures, and because the heat capacityof a gas with higher vapor content may be higher than the heat capacityof a gas with lower vapor content, less gas may be used in highertemperature areas of the humidifier and/or bubble column condenser tobetter balance the heat capacity rate ratios of the gas (e.g., air) andliquid (e.g., water) streams. Extraction and/or injection atintermediate locations may advantageously allow for manipulation of gasmass flows and for greater heat recovery. For example, a 30%intermediate extraction at 160° F. from a humidifier with a top moistair temperature of 180° F. and injection after the second stage in an8-stage bubble column can reduce energy consumption by about 40% toabout 50%.

It should be recognized that in some embodiments, under some operatingconditions, extraction may not increase the thermal efficiency of an HDHsystem. Additionally, there may be drawbacks associated with extractionat intermediate locations. For example, extraction may reduce the waterproduction rate of the system, and there may be significant monetarycosts associated with extraction (e.g., costs associated withinstrumentation, ducting, insulation, and/or droplet separation).Accordingly, in some cases, it may be advantageous to build and/oroperate a system without extraction.

In some embodiments, the HDH system further comprises an optionalcooling device. The cooling device may be any device that is capable ofremoving heat from a fluid stream, as described elsewhere herein. Insome embodiments, the cooling device is a heat exchanger. The heatexchanger may be configured such that a first fluid stream and a secondfluid stream flow through the heat exchanger. In some cases, the firstfluid stream and the second fluid stream may flow in substantially thesame direction (e.g., parallel flow), substantially opposite directions(e.g., counter flow), or substantially perpendicular directions (e.g.,cross flow). In some cases, heat is transferred from a first fluidstream to a second fluid stream. In certain embodiments, the coolingdevice is a liquid-to-gas heat exchanger. The first fluid stream may, incertain cases, comprise a fluid stream that is part of a loop ofcondenser liquid flowing between a condenser and a heat exchanger (e.g.,a condenser liquid outlet stream). The second fluid stream may, in somecases, comprise a coolant. The coolant may be any fluid capable ofabsorbing or transferring heat. In some embodiments, the coolantcomprises a gas. The gas may, in some cases, comprise air (e.g., ambientair). Heat exchangers that comprise air as a coolant may generally bereferred to as air-cooled heat exchangers. In some cases, more than twofluid streams flow through the cooling device. It should also be notedthat the cooling device may, in some embodiments, be a dry cooler, achiller, a radiator, or any other device capable of removing heat from afluid stream.

In some cases, the presence of a cooling device in an HDH system canadvantageously increase the amount of water recovered in the HDH system.In the absence of a cooling device, a fresh water stream entering adehumidifier may be cooled in a heat exchanger through transfer of heatto a cooled salt-containing water stream. In the absence of a coolingdevice, the temperature of the fresh water stream flowing through adehumidifier may therefore limited by the temperature of the brinestream. In the presence of a cooling device, the temperature of thefresh water entering the dehumidifier may no longer be limited by thetemperature of the brine stream, and lower temperatures may be achieved.Since air can generally hold less vapor at lower temperatures, morewater may be recovered at lower temperatures. In some cases, the coolingdevice may increase water production by at least about 5%, at leastabout 10%, at least about 20%, at least about 30%, at least about 40%,or at least about 50%. The inclusion of a cooling device may, in somecases, advantageously increase water production with a minimalconcomitant increase in electricity consumption.

In some embodiments, one fluid stream flowing through the cooling deviceis a condenser liquid stream. The condenser liquid stream may, in somecases, comprise purified water, which may be substantially pure water.For example, the condenser liquid stream may comprise part of a loop ofcondenser liquid (e.g., purified water) flowing between a condenser anda heat exchanger. In certain embodiments, one fluid stream flowingthrough the cooling device comprises air (e.g., ambient air). Thecooling device may be arranged, in some cases, such that the condenserliquid stream flows through the cooling device after flowing through aheat exchanger. In some cases, the cooling device may be arranged suchthat the condenser liquid stream flows through the cooling device beforeflowing through a dehumidifier (e.g., a bubble column condenser).

In some cases, the cooling device decreases the temperature of thecondenser liquid stream. In some embodiments, the cooling devicedecreases the temperature of the condenser liquid stream by at leastabout 5° C., at least about 10° C., at least about 15° C., at leastabout 20° C., at least about 30° C., at least about 40° C., at leastabout 50° C., at least about 60° C., at least about 70° C., at leastabout 80° C., or, in some cases, at least about 90° C. In someembodiments, the cooling device decreases the temperature of thecondenser liquid stream by an amount in the range of about 5° C. toabout 30° C., about 5° C. to about 60° C., about 5° C. to about 90° C.,about 10° C. to about 30° C., about 10° C. to about 60° C., about 10° C.to about 90° C., about 20° C. to about 60° C., about 20° C. to about 90°C., about 30° C. to about 60° C., about 30° C. to about 90° C., or about60° C. to about 90° C.

An exemplary embodiment of an HDH system comprising a cooling device isshown in FIG. 9. In FIG. 9, HDH system 900 comprises a humidifier 902, adehumidifier 904, a first reservoir of salt-containing water 906, asecond reservoir of salt-containing water 908, a reservoir of purifiedwater 910, a heat exchanger 912, an optional first heating device 914,an optional second heating device 916, and a cooling device 918.Humidifier 902 and dehumidifier 904 are arranged in fluid communicationvia gas conduits 930 and 932. In addition to being in fluidcommunication with dehumidifier 904, humidifier 902 is arranged to be influid communication with second reservoir of salt-containing water 908via liquid conduit 934. Humidifier 902 is also arranged to be in fluidcommunication with heat exchanger 912 via liquid conduit 936 andoptional first heating device 914 via liquid conduit 940. Dehumidifier904, in addition to being in fluid communication with humidifier 902, isarranged to be in fluid communication with reservoir of purified water910 via liquid conduit 942, optional second heating device 916 vialiquid conduit 944, and cooling device 918 via liquid conduit 950.Dehumidifier 904 may be a bubble column condenser as described herein.In some embodiments, cooling device 918 is arranged to be in fluidcommunication with heat exchanger 912 via liquid conduit 948. Coolingdevice 918 is also arranged to be in fluid communication with a gasstream (e.g., an air stream) through gas conduits 952 and 954. Firstreservoir of salt-containing water 906 is arranged to be in fluidcommunication with heat exchanger 912 via liquid conduit 956. Firstreservoir of salt-containing water 906 may also be fluidly connected toan external source of salt-containing water (e.g., from oil and/or gasproduction), not shown in FIG. 9.

In operation, a salt-containing water stream may flow from firstreservoir of salt-containing water 906 to heat exchanger 912. Heat maybe transferred from another fluid stream (e.g., a condenser liquidstream) to the salt-containing water stream, resulting in a heatedsalt-containing water stream. The heated salt-containing water streammay then flow to optional first heating device 914 via liquid conduit938 to be further heated. The further heated salt-containing waterstream may be directed to flow to humidifier 902 via liquid conduit 940.In humidifier 902, at least a portion of water may be evaporated to acarrier gas stream flowing through humidifier 902 counterflow to thesalt-containing water stream. A first portion of the remainingsalt-containing water that is not evaporated may then flow to secondsalt-containing reservoir 908 via liquid conduit 934. A second portionof the remaining salt-containing water that is not evaporated may berecirculated to heat exchanger 912 via liquid conduit 936.

A carrier gas stream may flow in a direction opposite that of thesalt-containing water stream. The carrier gas stream may enterhumidifier 902 and come into contact with the heated salt-containingwater stream. Water may be evaporated to the carrier gas stream, therebyresulting in a humidified carrier gas stream. The humidified carrier gasstream may flow to dehumidifier 904 via gas conduit 930. In dehumidifier904, the humidified carrier gas stream may come into contact with achilled condenser liquid stream flowing in the opposite direction. Heatand mass may be transferred from the humidified carrier gas stream tothe chilled condenser liquid stream as water is condensed from thehumidified carrier gas stream, resulting in a dehumidified carrier gasstream. The dehumidified carrier gas stream may be flowed to humidifier902 via gas conduit 932.

A condenser fluid (e.g., water) stream may flow through dehumidifier 904counterflow to the carrier gas stream. As the condenser fluid streamflows through dehumidifier 904, water may be condensed from thehumidified carrier gas stream to the condenser liquid stream, therebyresulting in a condenser liquid outlet stream. At least a portion of thecondenser liquid outlet stream may flow through liquid conduit 942 toreservoir of purified water 910. At least a portion of the condenserliquid outlet stream may flow through optional second heating device 916via liquid conduit 944. In optional second heating device 914, thecondenser liquid outlet stream may be heated, resulting in a heatedcondenser liquid outlet stream. In some cases, the heated condenserliquid outlet stream may flow to heat exchanger 912 via liquid conduit946. In heat exchanger 912, the heated condenser liquid outlet streammay transfer heat to the salt-containing water stream, resulting in achilled condenser liquid outlet stream. The chilled condenser liquidoutlet stream may then flow to cooling device 918 via liquid conduit948. A gas stream may also flow through cooling device 918. The twostreams may flow parallel, counter flow, or cross flow to each other. Insome embodiments, the gas stream comprises air. The air may, forexample, enter cooling device 918 through gas conduit 952 and exitcooling device 918 through gas conduit 954. In some embodiments, heatmay be transferred from the chilled condenser liquid outlet stream tothe air, resulting in a further chilled condenser liquid outlet stream.The further chilled condenser liquid outlet stream may then be flowed todehumidifier 904 through liquid conduit 950.

Example 1

In the following example, an 8-stage bubble column condenser and a heatexchanger for use in a humidification-dehumidification system aredescribed. As shown in FIG. 5, system 500 includes custom-designedcondenser 502 and heat exchanger 504 in fluid communication with oneanother. The exterior of the condenser comprises stainless steel, andthe condenser has the shape of a rectangular prism. Eight stages, asdescribed herein, are arranged vertically within the bubble condenser,with a sump volume 506 located beneath the stages in fluid communicationwith a liquid outlet 508. Each stage comprises a sparger plate (1.8 mlong, 0.6 m wide, and 0.06 m tall, having a plurality of holes with adiameter of about 0.003 m) and a chamber in which a liquid bath canreside. A first gas inlet 510 is positioned below the sparger platelocated near the bottom of the bubble column condenser, and a second gasinlet 512 is positioned at an intermediate location between. Above thetopmost stage, a liquid inlet 514 and a mist eliminator (e.g., dropleteliminator) 516 that is coupled to a first gas outlet 518 are arranged.

Bubble column condenser 502 is coupled to heat exchanger 504, which hastwo conduits 520 and 522. First conduit 520 is fluidically connected toliquid inlet 514 and outlet 508 of the bubble column condenser. Secondconduit 522 is fluidically connected to other components of ahumidification-dehumidification system.

When the humidification-dehumidification system (i.e., containing the8-stage bubble column condenser and heat exchanger as described) is inoperation, a first stream of dry air enters the bubble column throughfirst gas inlet 510 at a temperature of about 88° C., 100% relativehumidity, a volumetric flow rate of 4,992 cubic feet per minute (cfm),and a mass flow rate of 14,241 lbs/hr. A second stream of dry air entersthe bubble column condenser through second gas inlet 512 at atemperature of about 77° C., 100% relative humidity, a volumetric flowrate of 1,697 cfm, and a mass flow rate of 5,777 lbs/hour. A liquidstream enters the condenser at liquid inlet 514, at a temperature ofabout 45° C., a volumetric flow rate of 187.6 gallons per minute (gpm),and a mass flow rate of 93.8 lbs/hr. During operation, a gas outletstream and a liquid outlet stream are produced as described herein. Thegas outlet stream exits at gas outlet 518 at a temperature of about 49°C., a volumetric flow rate of about 3272 cfm, and a mass flow rate of12,819 lbs/hr. The liquid outlet stream exits the bubble columncondenser and is pumped by a column circulation pump 524 at a volumetricflow rate of 202 gallons per minute and a mass flow rate of 101,064lbs/hour. The liquid outlet stream passes through one conduit of theheat exchanger. Heat is transferred from the liquid outlet stream to asalt-containing water stream flowing through conduit 522 of the heatexchanger (e.g., the stream that is heated by the condenser liquidoutlet stream in the heat exchanger). The salt-containing water streamenters the heat exchanger at about 42° C., a volumetric flow rate of196.3 GPM, and a mass flow rate of 118,703 lbs/hr, and leaves at about81° C., a volumetric rate of 196.3 GPM, and a mass flow rate of 118,703lbs/hr. A portion of the liquid outlet stream is directed to asubstantially pure water reservoir via valve 526 at a temperature ofabout 45° C., a volumetric flow rate of 14.58 gallons per minute, and amass flow rate of about 7,289 lbs/hr. The remaining portion of theliquid outlet stream returns to condenser 502 through liquid inlet 514.While the system is undergoing substantially continuous operation, eachstage of the bubble column condenser contains about 0.1 m or less ofwater.

Table 1 lists the constituents of a salt-containing water stream priorto and after treatment (e.g., desalination) using thehumidification-dehumidification system described in this Example. It isnoted that the concentrations of calcium and magnesium appeared toincrease after treatment. This may be due to the bubble column initiallybeing supplied with local drinking water (e.g., from Midland, Tex.). Thelocal drinking water was hard and had relatively high concentrations ofcalcium and magnesium. As a result, trace amounts of calcium and/ormagnesium may have remained in the bubble column during testing, andtrace amounts of the elements may have been present in the desalinationeffluent (e.g., the water stream after treatment). In contrast,pretreatment systems upstream of the desalination system may haveremoved almost all of the calcium and magnesium from the feed waterstream (e.g., the water stream before treatment). Accordingly, the waterstream after treatment may have contained higher concentrations ofcalcium and magnesium than the water stream before treatment.

An additional exemplary embodiment of an 8-stage bubble column condenseris shown in FIG. 7. In FIG. 7A, bubble column condenser 700 comprisesgas inlets 702 and 704, gas outlet 706, and liquid inlet 708. FIG. 7Bshows another view of condenser 700, which comprises eight stages asdescribed herein. FIGS. 7C-I show additional views of the bubble columncondenser and its components.

TABLE 1 Salt-containing water profile before and after treatment (i.e.,desalination). Concentration Before Concentration After ConstituentTreatment Treatment Oil and Grease ND ND Total Suspended Solids 57 mg/LND Total Dissolved Solids 28,400 mg/L 35 mg/L Barium .701 mg/L .005 mg/LBromide 1050 mg/L 1.16 mg/L Calcium ND 7.08 mg/L Chloride 13,300 mg/L5.0 mg/L Sulfate 1020 mg/L 5.1 mg/L Magnesium ND 0.775 mg/L Aluminum37.5 mg/L 0.077 mg/L Sodium 11,800 mg/L 3.09 mg/L Strontium 67 mg/L0.079 ppm Zinc ND ND Benzene 37.5 ug/L ND Toluene 32.1 ug/L NDAlkalinity (CaCO3) 3260 mg/L ND Recovery Ratio — 82% (ND = Notdeterminable)

Example 2

In this example, an 8-stage bubble column condenser and an external heatexchanger for use in a humidification-dehumidification system aredescribed.

As shown in FIG. 10A, system 1000 comprised an 8-stage bubble columncondenser 1002 and a heat exchanger 1004, which were in fluidcommunication with each other. Condenser 1002 and heat exchanger 1004were also in fluid communication with a humidifier (not shown). Incondenser 1002, eight stages 1002A, 1002B, 1002C, 1002D, 1002E, 1002F,1002G, and 1002H were arranged vertically within the condenser. Abovetopmost stage 1002A, a liquid inlet 1006 and a gas outlet 1022 werearranged. A sump volume 1002I was located at the bottom of condenser1002, beneath the bottommost stage. Sump volume 1002I was in fluidcommunication with a liquid outlet 1008. In addition, condenser 1002further comprised a first gas inlet 1018 positioned near the bottom ofcondenser 1002 and a second gas inlet 1020 positioned at an intermediatelocation, between the top and bottom of condenser 1002.

In operation, a stream of substantially pure water entered condenser1002 through liquid inlet 1006 and flowed downward through each stage ofcondenser 1002. A stream of humidified carrier gas flowed counterflow tothe substantially pure water stream, entering condenser 1002 through gasinlets 1018 and 1020 and flowing upwards through condenser 1002. As thetwo streams flowed through condenser 1002, heat and mass weretransferred from the humidified carrier gas stream to the substantiallypure water stream. As a result, the temperature of the substantiallypure water stream increased as it flowed through each stage. Inuppermost stage 1002A, the temperature of the water stream was 141.6° F.The temperature in stage 1002B was 148.3° F., the temperature in stage1002C was 154.7° F., the temperature in stage 1002D was 161.5° F., thetemperature in stage 1002E was 166.8° F., the temperature in 1002F was170.1° F., the temperature in stage 1002G was 172.1° F., and thetemperature in stage 1002H was 172.8° F. Sump volume 1002I, located atthe bottom of condenser 1002, had 7.7 inches of water. The substantiallypure water stream then exited condenser 1002 through liquid outlet 1008at a temperature of 173.4° F.

As the substantially pure water stream exited condenser 1002, a pump(not shown) operating at 68.6% capacity pumped the water stream to heatexchanger 1004 at a volumetric flow rate of 180.8 gallons per minute. Asthe substantially pure water stream flowed through heat exchanger 1004,heat was transferred from the substantially pure water stream to anotherfluid stream flowing through heat exchanger 1004, and the temperature ofthe substantially pure water stream was reduced from 173.4° F. to 142.7°F. After flowing through heat exchanger 1004 and becoming chilled, afirst portion of the chilled substantially pure water stream was flowedthrough liquid conduit 1012 to a purified water reservoir (not shown),and a second portion of the chilled substantially pure water streamreturned to condenser 1002 via conduit 1010 through liquid inlet 1006.

In heat exchanger 1004, a salt-containing water stream was flowedcounterflow to the substantially pure water stream. Initially, thesalt-containing water stream flowed from a source of salt-containingwater through liquid conduit 1014. As it entered heat exchanger 1004,the salt-containing water stream was at a temperature of 121.3° F. and apressure of 43.4 psi. After flowing through heat exchanger 1004 andreceiving heat transferred from the substantially pure water stream, thetemperature of the salt-containing water stream increased to 165.0° F.The pressure of the salt-containing water stream was 40.1 psi. Theheated salt-containing water stream was then flowed to the humidifier.

Example 3

This example describes the 8-stage bubble column condenser and externalheat exchanger of Example 2, with the addition of an external coolingdevice.

As shown in FIG. 10B, system 1000 comprised all the components shown inFIG. 10A and further comprised an external cooling device 1024 in fluidcommunication with bubble column condenser 1002 and heat exchanger 1004.

In operation, a stream of substantially pure water entered condenser1002 through liquid inlet 1006 and flowed downward through each stage ofcondenser 1002. A stream of humidified carrier gas flowed counterflow tothe substantially pure water stream, entering condenser 1002 through gasinlets 1018 and 1020 and flowing upwards through condenser 1002. As thetwo streams flowed through condenser 1002, heat and mass weretransferred from the humidified carrier gas stream to the substantiallypure water stream. As a result, the temperature of the substantiallypure water stream increased as it flowed through each stage. Inuppermost stage 1002A, the temperature of the water stream was 124.8° F.The temperature in stage 1002B was 133.6° F., the temperature in stage1002C was 148.2° F., the temperature in stage 1002D was 158.6° F., thetemperature in stage 1002E was 167.1° F., the temperature in 1002F was171.6° F., the temperature in stage 1002G was 174.4° F., and thetemperature in stage 1002H was 175.3° F. Sump volume 1002I, located atthe bottom of condenser 1002, had 9.3 inches of water. The substantiallypure water stream then exited condenser 1002 through liquid outlet 1008at a temperature of 175.4° F.

As the substantially pure water stream exited condenser 1002, a pump(not shown) operating at 72.7% capacity pumped the water stream to heatexchanger 1004 at a volumetric flow rate of 191.0 gallons per minute. Asthe substantially pure water stream flowed through heat exchanger 1004,heat was transferred from the substantially pure water stream to anotherfluid stream flowing through heat exchanger 1004, and the temperature ofthe substantially pure water stream was reduced from 175.4° F. to 145.8°F. After flowing through heat exchanger 1004 and becoming chilled, afirst portion of the chilled substantially pure water stream was flowedthrough liquid conduit 1012 to a purified water reservoir (not shown). Asecond portion of the chilled substantially pure water stream was flowedthrough a cooling device 1024. In cooling device 104, the second portionof the chilled substantially pure water stream was further chilled, andthe temperature of the second portion of the chilled substantially purewater stream was further reduced to 120° F. The further chilledsubstantially pure water stream was then returned to condenser 1002 viaconduit 1010 through liquid inlet 1006.

In heat exchanger 1004, a salt-containing water stream was flowedcounterflow to the substantially pure water stream. Initially, thesalt-containing water stream flowed from a source of salt-containingwater through liquid conduit 1014. As it entered heat exchanger 1004,the salt-containing water stream was at a temperature of 133.8° F. and apressure of 48.7 psi. After flowing through heat exchanger 1004 andreceiving heat transferred from the substantially pure water stream, thetemperature of the salt-containing water stream increased to 164.9° F.The pressure of the salt-containing water stream was 44.9 psi. Theheated salt-containing water stream was then flowed to the humidifier.

Example 4

As shown in FIG. 11A, this example describes an HDH system 1100, whichcomprises a humidifier 1102, a multi-stage bubble column condenser 1104,an external heat exchanger 1106, an external heating device 1108, and anexternal cooling device 1110.

In operation, a brine stream enters heat exchanger 1106, which is aplate-and-frame heat exchanger, at a flow rate of 620 gallons per minute(gpm) and a temperature of 130° F. In heat exchanger 1106, heat istransferred from a hot fresh water stream exiting condenser 1104 to thebrine stream, and the temperature of the brine stream is increased by30° F., from 130° F. to 160° F. This step advantageously recovers energyfrom the hot fresh water stream and reduces the amount of heat requiredto be supplied by heating device 1108.

The heated brine stream then flows through liquid conduit 1112 andenters heating device 1108 at a flow rate of 625 gpm and a temperatureof 160° F. As the heated brine stream flows through heating device 1108,which is a plate-and-frame heat exchanger, heat is transferred from astream of hot, pressurized water to the heated brine stream, resultingin the heated brine stream being further heated to a temperature of 200°F.

The further heated brine stream then flows through liquid conduit 1114and enters humidifier 1102 at a flow rate of 632 gpm and a temperatureof 200° F. As the further heated brine stream flows in a first directionfrom a brine inlet located at a first end (e.g., a top end) ofhumidifier 1102 to a brine outlet located at a second end (e.g., abottom end) of humidifier 1102, the brine stream comes into directcontact with a stream of ambient air flowing in a second, substantiallyopposite direction through humidifier 1102. The stream of ambient airenters humidifier 1102 at a flow rate of 8,330 actual cubic feet perminute (acfm) and a temperature of 60° F. As the stream of ambient airflows in the second direction through humidifier 1102, heat and mass aretransferred from the further heated brine stream to the ambient airstream, resulting in a humidified air stream and a concentrated brinestream. The concentrated brine stream exits humidifier 1102 at a flowrate of 593 gpm and a temperature of 135° F. and is subsequentlydischarged from HDH system 1100 via conduit 1116.

The humidified air stream exits humidifier 1102 through a mainhumidifier air outlet and flows through gas conduit 1118 to multi-stagebubble condenser 1104. The humidified air stream enters condenser 1104through a main condenser humidified air inlet at a flow rate of 15,000acfm and a temperature of 173° F. In condenser 1104, the humidified airstream comes into direct contact with a fresh water stream, which enterscondenser 1104 through a condenser fresh water inlet at a flow rate of550 gpm and a temperature of 125° F. In condenser 1104, heat and massare transferred from the humidified air stream to the fresh water streamas water is condensed from the humidified air stream, resulting in adehumidified air stream and a heated fresh water stream. Thedehumidified air stream exits condenser 1104 through a condenser airoutlet at a flow rate of 9,500 acfm and a temperature of 127° F. Theheated fresh water stream exits condenser 1104 through a condenser freshwater outlet at a flow rate of 575 gpm and a temperature of 170° F. Theheated fresh water stream then flows through heat exchanger 1106, whereheat is transferred from the heated fresh water stream to the brinestream entering HDH system 1100, resulting in a cooled fresh waterstream and the heated brine stream. After flowing through heat exchanger1106, a first portion of the cooled fresh water stream exits HDH system1100 via a condenser condensate outlet at a flow rate of 25 gpm and atemperature of 140° F. A second portion of the fresh water stream flowsto cooling device 1110, which is an air-cooled heat exchanger. As thecooled fresh water stream flows through cooling device 1110, heat istransferred from the cooled fresh water stream to a stream of air, andthe cooled fresh water stream is further cooled to a temperature of 125°F. The further cooled fresh water stream then returns to condenser 1104through a condenser fresh water inlet at a flow rate of 550 gpm and atemperature of 125° F.

Example 5

This example describes the HDH system 1100 of Example 3, with theaddition of an intermediate gas conduit 1122 connecting humidifier 1102and condenser 1104. When this system, which is shown in FIG. 11B, is inoperation, air is extracted from humidifier 1102 at an intermediate airoutlet. The air subsequently flows through intermediate gas conduit 1122and is injected directly into an intermediate location in condenser1104. The locations of the extraction and injection points are selectedin order to optimize the thermal efficiency of the system. Because theintermediate air stream is extracted from humidifier 1102 before thestream has flowed through the entire humidifier, the temperature of theintermediate air stream is lower than the temperature of the humidifiedair stream exiting humidifier 1102 through a main humidifier air outlet.For example, while the humidified air stream exiting humidifier 1102through the main air outlet enters condenser 1104 at a flow rate of12,000 acfm and a temperature of 173° F., the intermediate air streamexiting humidifier 1102 through the intermediate air outlet enterscondenser 1104 at a flow rate of 8,000 acfm and a temperature of 160° F.

Example 6

This example describes an HDH system 1100 comprising a humidifier 1102,a multi-stage bubble column condenser 1124 comprising an internal heatexchanger, an external heating device 1108, and an external coolingdevice 1110. This system is shown in FIG. 11C.

When HDH system 1100 is in operation, a brine stream enters the internalheat exchanger of condenser 1124 at a flow rate of 620 gpm and atemperature of 115° F. As the brine stream flows through the internalheat exchanger of condenser 1124, heat is transferred to the brinestream from a fresh water stream flowing through condenser 1124,resulting in a heated brine stream that exits condenser 1124 at a flowrate of 625 gpm and a temperature of 160° F. The heated brine streamthen flows through liquid conduit 1112 to heating device 1108, where theheated brine stream is further heated to a temperature of 200° F. Thefurther heated brine stream then flows through conduit 1114 and entershumidifier 1102 at a flow rate of 632 gpm and a temperature of 200° F.

In humidifier 1102, the further heated brine stream comes into directcontact with an ambient air stream, which enters humidifier 1102 at aflow rate of 8,330 acfm and a temperature of 80° F. Heat and mass aretransferred from the further heated brine stream to the ambient airstream, resulting in a humidified air stream and a concentrated brinestream. The concentrated brine stream exits humidifier 1102 at a flowrate of 593 gpm and a temperature of 135° F. A first portion of theconcentrated brine stream exits HDH system 1100, and a second portion ofthe concentrated brine stream flows to cooling device 1110, where theconcentrated brine stream is cooled to a temperature of 120° F. Thecooled brine stream exits cooling device 1110 at a flow rate of 593 gpmand a temperature of 120° F. The cooled brine stream is combined with astream of incoming brine, which enters at a flow rate of 25 gpm and atemperature of 60° F., before returning to condenser 1124 at atemperature of 115° F.

The humidified air stream exits a main air outlet of humidifier 1102 andenters condenser 1124 at a flow rate of 15,000 acfm and a temperature of173° F. In condenser 1124, the humidified air stream comes into contactwith the fresh water stream, and purified water is condensed from thehumidified air stream, resulting in a dehumidified air stream. Thepurified water enters the fresh water stream, which exits condenser 1124at a flow rate of 25 gpm and a temperature of 170° F. The dehumidifiedair stream exits condenser 1124 at a flow rate of 9500 acfm and atemperature of 127° F.

Example 7

This example describes the HDH system 1100 of Example 5, with theaddition of an intermediate gas conduit 1122 connecting humidifier 1102and condenser 1124. When this system, which is shown in FIG. 11D, is inoperation, air is extracted from humidifier 1102 at an intermediate airoutlet. The air subsequently flows through intermediate gas conduit 1122and is injected directly into an intermediate location in condenser1124. The locations of the extraction and injection points are selectedin order to optimize the thermal efficiency of the system. Because theintermediate air stream is extracted from humidifier 1102 before thestream has flowed through the entire humidifier, the temperature of theintermediate air stream is lower than the temperature of the humidifiedair stream exiting humidifier 1102 through a main humidifier air outlet.For example, while the humidified air stream exiting humidifier 1102through the main air outlet enters condenser 1124 at a flow rate of12,000 acfm and a temperature of 173° F., the intermediate air streamexiting humidifier 1102 through the intermediate air outlet enterscondenser 1104 at a flow rate of 8,000 acfm and a temperature of 160° F.

Having thus described several aspects of some embodiments of thisinvention, it is to be appreciated various alterations, modifications,and improvements will readily occur to those skilled in the art. Suchalterations, modifications, and improvements are intended to be part ofthis disclosure, and are intended to be within the spirit and scope ofthe invention. Accordingly, the foregoing description and drawings areby way of example only.

What is claimed is:
 1. A humidifier system, comprising: a humidifierapparatus, comprising: a vessel comprising a liquid inlet in fluidcommunication with a source of a liquid comprising a condensable fluidin liquid phase, a liquid outlet, and at least one chamber in fluidcommunication with the liquid inlet and the liquid outlet, wherein theat least one chamber comprises a bottom surface comprising a pluralityof perforations through which vapor can travel; a liquid layerpositioned in contact with the liquid outlet, wherein the liquid layercomprises an amount of the liquid comprising the condensable fluid inliquid phase; a vapor distribution region positioned below the at leastone chamber, the vapor distribution region comprising a vapor inlet influid communication with a source of a vapor mixture comprising thecondensable fluid in vapor phase and/or a non-condensable gas; and avapor outlet arranged in fluid communication with the at least onechamber; and a liquid-to-liquid heat exchanger positioned external tothe vessel and fluidly connected to the liquid inlet and the liquidoutlet of the vessel, wherein the heat exchanger receives and deliversheat to the liquid comprising the condensable fluid in liquid phaseprior to entry of the liquid comprising the condensable fluid in liquidphase into the liquid inlet of the vessel, wherein: the humidifierapparatus produces a vapor-containing humidifier gas outlet streamenriched in the condensable fluid in vapor phase relative to the vapormixture received from the vapor inlet, and the vapor-containinghumidifier gas outlet stream exits the vessel through the vapor outlet,and the humidifier apparatus produces a liquid-containing streamcontaining an amount of the condensable fluid in liquid phase, theliquid-containing stream exits the vessel through the liquid outlet, andat least a portion of the liquid-containing stream that exits the vesselthrough the liquid outlet flows through the liquid-to-liquid heatexchanger and is returned to the vessel through the liquid inlet.
 2. Thehumidifier system of claim 1, wherein the condensable fluid compriseswater.
 3. The humidifier system of claim 1, wherein the vapor mixturecomprises air.
 4. The humidifier system of claim 1, wherein thehumidifier apparatus further comprises a second vapor distributionregion comprising a vapor inlet in fluid communication with a source ofa vapor mixture comprising the condensable fluid in vapor phase and/or anon-condensable gas.
 5. The humidifier system of claim 1, wherein the atleast one chamber has an aspect ratio of at least about 1.5.
 6. Thehumidifier system of claim 1, wherein the humidifier apparatus has asubstantially rectangular cross section.
 7. The humidifier system ofclaim 1, wherein the humidifier apparatus has a substantiallyparallelepiped shape.
 8. The humidifier system of claim 1, wherein theat least one chamber comprises a first weir and a second weir positionedalong a bottom surface of the chamber, wherein the first weir and secondweir each have a height that is less than the height of the chamber, thefirst and second weirs being arranged such that a stream of the liquidcomprising the condensable fluid in liquid phase flows across thechamber from the first weir to the second weir.
 9. The humidifier systemof claim 8, wherein at least one of the first and second weirs has aheight of about 0.08 m or less.
 10. The humidifier system of claim 1,wherein the at least one chamber comprises at least one longitudinalbaffle positioned along a bottom surface of the chamber.
 11. Thehumidifier system of claim 1, wherein the humidifier apparatus furthercomprises a first chamber and a second chamber arranged in a verticalmanner with respect to one another and in fluid communication with theliquid inlet and the liquid outlet, wherein the first and secondchambers are arranged such that the liquid comprising the condensablefluid in liquid phase flows across the length of the first chamber in afirst direction and across the length of the second chamber in a second,opposing direction.
 12. A humidifier apparatus, comprising: a vesselcomprising: a liquid inlet in fluid communication with a source of aliquid comprising a condensable fluid in liquid phase; a liquid outlet;and at least one chamber in fluid communication with the liquid inletand the liquid outlet, the at least one chamber comprising: a bottomsurface comprising a plurality of perforations through which vapor cantravel; and a first weir and a second weir positioned along the bottomsurface of the chamber, wherein the first weir and second weir each havea height that is less than the height of the chamber, and are arrangedsuch that a stream of the liquid comprising the condensable fluid inliquid phase flows across the chamber from the first weir to the secondweir, and wherein the second weir has a height of about 0.08 m or less;a liquid layer positioned in contact with the liquid outlet, wherein theliquid layer comprises an amount of the liquid comprising thecondensable fluid in liquid phase; a vapor distribution regionpositioned below the at least one chamber, the vapor distribution regioncomprising a vapor inlet in fluid communication with a source of a vapormixture comprising the condensable fluid in vapor phase and/or anon-condensable gas; and a vapor outlet arranged in fluid communicationwith the at least one chamber, wherein: the humidifier apparatusproduces a vapor-containing humidifier gas outlet stream enriched in thecondensable fluid in vapor phase relative to the vapor mixture receivedfrom the vapor inlet, and the vapor-containing humidifier gas outletstream exits the vessel through the vapor outlet, and the humidifierapparatus produces a liquid-containing stream containing an amount ofthe condensable fluid in liquid phase, the liquid-containing streamexits the vessel through the liquid outlet, and at least a portion ofthe liquid-containing stream that exits the vessel through the liquidoutlet is returned to the vessel through the liquid inlet.
 13. Thehumidifier apparatus of claim 12, wherein the condensable fluidcomprises water.
 14. The humidifier apparatus of claim 12, wherein thevapor mixture comprises air.
 15. The humidifier apparatus claim 12,further comprising a second vapor distribution region comprising a vaporinlet in fluid communication with a source of a vapor mixture comprisingthe condensable fluid in vapor phase and/or a non-condensable gas. 16.The humidifier apparatus of claim 12, wherein the at least one chamberhas an aspect ratio of at least about 1.5.
 17. The humidifier apparatusof claim 12, wherein the humidifier apparatus has a substantiallyrectangular cross section.
 18. The humidifier apparatus of claim 12,wherein the humidifier apparatus has a substantially parallelepipedshape.
 19. The humidifier apparatus of claim 12, wherein the at leastone chamber comprises at least one longitudinal baffle positioned alonga bottom surface of the chamber.
 20. The humidifier apparatus of claim12, further comprising a first chamber and a second chamber arranged ina vertical manner with respect to one another and in fluid communicationwith the liquid inlet and the liquid outlet, wherein the first andsecond chambers are arranged such that the liquid comprising thecondensable fluid in liquid phase flows across the length of the firstchamber in a first direction and across the length of the second chamberin a second, opposing direction.